<PAGE>   1
                                                                   Exhibit 10.63


                        TWENTY FIRST AMENDMENT AND WAIVER


         TWENTY FIRST AMENDMENT AND WAIVER (this "Amendment"), dated as of May
18, 2000, among ANCHOR GLASS CONTAINER CORPORATION, f/k/a Anchor Glass
Acquisition Corporation, a Delaware Corporation (the "Borrower"), the financial
institutions party to the Credit Agreement referred to below (the "Lenders"),
BANKERS TRUST COMPANY ("BTCo"), BT COMMERCIAL CORPORATION ("BTCC"), and PNC
BANK, NATIONAL ASSOCIATION, as Co-Syndication Agent and as an Issuing Bank (an
"Issuing Bank"). All capitalized terms used herein and not otherwise defined
shall have the respective meanings provided such terms in the Credit Agreement
referred to below.


                              W I T N E S S E T H :


         WHEREAS, the Borrower, the Lenders, the Issuing Banks, BTCo and BTCC
are parties to a Credit Agreement, dated as of February 5, 1997 (as amended,
modified or supplemented through the date hereof, the "Credit Agreement");

         WHEREAS, the Borrower is in Default under Section 8.4 of the Credit
Agreement because it exceeded the capital expenditure limitations provided
therein for the year ended December 31, 1999;

         WHEREAS, G&G Investments, Inc. ("G&G") is in default under Section
4.1(a) of the Guaranty and Pledge Agreement, dated as of September 8, 1998 (as
amended, modified or supplemented through the date hereof, the "Pledge
Agreement") between the G&G Investments, Inc., as the guarantor and pledgor, and
BT Commercial Corporation, as collateral agent and pledgee, because it is unable
to provide all of the additional Consumers Stock (as such term is defined in the
Pledge Agreement) required therein when the market value of the Consumers Stock
falls; and

         WHEREAS, the parties hereto wish to amend certain provisions of the
Credit Agreement and waive certain Defaults under the Credit Agreement and
Pledge Agreement as herein provided, subject to and on the terms and conditions
set forth herein;

         NOW, THEREFORE, it is agreed:

         1. Section 1.1 of the Credit Agreement is hereby amended by inserting
the following new definitions into their appropriate alphabetical order:

         "O-I Litigation shall mean any and all disputes, actions or
proceedings, including arbitration, which may arise from O-I's allegations that
the License Agreement has been terminated and/or any related notices.




<PAGE>   2

         Steering Committee shall mean a committee comprised of a portion of the
Lenders under this Credit Agreement established and appointed to perform certain
of the duties customarily performed by the Agent.

         Twenty First Amendment Effective Date shall have the meaning provided
in the Twenty First Amendment and Waiver to the Credit Agreement, dated May 18,
2000."

         2. The definition of Applicable Margin contained in Section 1.1 of the
Credit Agreement is hereby amended by (i) replacing the "and" after the phrase
"(ii) at any time when any Default or Event of Default is in existence, Level
IV" with a comma, (ii) inserting the phrase "during the period on and after the
Twenty First Amendment Effective Date until July 31, 2000, the applicable Level
for such period as determined below plus an additional 25 basis points" and
(iv)" after "(iii)", (iii) replacing the "and" appearing after the phrase "at
any time other than those periods referred to in the clauses (i)" with a comma
and inserting "and (iii)" after the phrase "at any time other than those periods
referred to in the clauses (i), (ii)", so that the definition of Applicable
Margin will now read as follows:

         "Applicable Margin shall mean the applicable percentage set forth below
based upon (x) (i) during the period from the Closing Date until the Test Period
ended December 31, 1997, Level III, (ii) at any time when any Default or Event
of Default is in existence, Level IV, (iii) during the period on and after the
Twenty First Amendment Effective Date until July 31, 2000, the applicable Level
for such period as determined below plus an additional 25 basis points and (iv)
at any time other than those periods referred to in clauses (i), (ii) and (iii)
above, the Level for such Quarterly Period and (y) the Outstandings hereunder as
a percentage of the Available Borrowing Amount for such Quarterly Period:

<TABLE>
<CAPTION>

                          Outstandings Do Not Exceed                   Outstandings Equal or Exceed
                      50% of Available Borrowing Amount             50% of Available Borrowing Amount
                      ---------------------------------             ---------------------------------

                      Eurodollar                 Base                Eurodollar               Base
  Level               Rate Loan               Rate Loan              Rate Loan              Rate Loan
                      ----------              ---------              ----------             ---------
<S>                   <C>                     <C>                    <C>                    <C>
Level I                 1.50%                   .00%                   1.75%                  0.25%
Level II                1.75%                   .25%                   2.00%                  0.50%
Level III               2.00%                   .50%                   2.25%                  0.75%
Level IV                2.25%                   .75%                   2.50%                  1.00%
</TABLE>

The Leverage Ratio and Outstandings shall be determined based on the Financial
Statements delivered pursuant to Sections 7.1(a) and (b) for the fiscal quarter
ended immediately prior to the relevant Start Date. The Applicable Margin so
determined shall apply from the Start Date to the End Date. If no Financial
Statements shall have been delivered to the Agent on or prior to the relevant
End Date, the Applicable Level shall be Level IV until such Financial Statements
are delivered."




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         3. The Default under Section 8.4 of the Credit Agreement which arose as
a result of the Borrower exceeding the capital expenditure limitations provided
therein for the year ended December 31, 1999 is hereby waived.

         4. The Default under Section 4.1(a) of the Pledge Agreement which arose
as a result of G&G being unable to produce shares of Consumers Stock (as such
term is defined in the Pledge Agreement) above the amount being delivered
pursuant to Section 13 of this Amendment is hereby waived and any future default
under Section 4.1(a) which results from the inability of G&G to produce
additional Consumers Stock due to a drop in the market value of Consumers Stock
is hereby waived, in each case only to the extent that G&G holds no additional
shares of Consumers Stock.

         5. Section 2.3(c) is hereby amended by deleting the phrase "or the
forty fifth Business Day after such date for Agent Advances resulting from any
Default under Section 8.4 prior to March 10, 2000" which appears after the
phrase "or until June 15, 2000 for Agent Advances resulting from any Default
under Section 8.4 prior to March 10, 2000"

         6. Section 7.1 of the Credit Agreement is hereby amended by (i)
deleting the "and" which appears at the end of Section 7.1(i)(iv), (ii)
replacing the period which appears at the end of Section 7.1(j) with "; and" and
(ii) inserting the following provision:

         "(k) weekly the Borrower shall provide written progress reports to the
Steering Committee on the status of the O-I Litigation and on the status of the
Southeast Project until such time as the Steering Committee determines that such
reports are no longer necessary."

         7. Article 8 of the Credit Agreement is hereby amended by inserting the
following provisions:

         "8.27 SAP Computer Conversion. The Borrower shall not make any further
payments, whether the payments are contractual obligations, dividends or
otherwise, after the Twenty First Amendment Effective Date to Consumers
Packaging Inc. and/or any third party with respect the SAP computer conversion."

         8. Section 8.25 is hereby amended by (i) deleting the word "until"
which appears after the amount "$12,500,000", (ii) inserting the phrase "(except
that for the period on and after the Twenty First Amendment Effective Date until
July 31, 2000, the Available Borrowing Amount less the Outstandings shall not be
permitted to be less than $7,500,000 unless either proviso set forth below is in
effect); provided that, after" after the phrase "The Available Borrowing Amount
less the Outstandings shall not be permitted to be less than $12,500,000", (iii)
deleting "; thereafter" after the amount "$24,000,000", (iv) replacing the word
"until" which appears after the amount "$6,000,000" with the phrase "; provided
further, if in addition" and (v) inserting the phrase "the Available Borrowing
Amount less the Outstandings shall not be permitted to be less than zero", so
that the paragraph will now read as follows:

         8.25 Minimum Availability. The Available Borrowing Amount less the
Outstandings shall not be permitted to be less than $12,500,000 (except that for
the period on and




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after the Twenty First Amendment Effective Date until July 31, 2000, the
Available Borrowing Amount less the Outstandings shall not be permitted to be
less than $7,500,000 unless either proviso set forth below is in effect);
provided that, after the initial funding of the sale and leaseback of the
Southeast Project is consummated in compliance with this Agreement and the
Borrower has received and notified the Agent of receipt of proceeds in the
amount of $24,000,000, the Available Borrowing Amount less the Outstandings
shall not be permitted to be less than $6,000,000; provided further, if in
addition the Borrower has received a signed commitment for at least an
additional $50,000,000 of financing for the Southeast Project under terms and
conditions, and pursuant to documentation, satisfactory to the Agent, the
Available Borrowing Amount less the Outstandings shall not be permitted to be
less than zero."

         9. In order to induce the Lenders to enter into this Amendment and
Waiver, the Borrower hereby represents and warrants that (i) the
representations, warranties and agreements contained in Article 6 of the Credit
Agreement are true and correct in all material respects on and as of the Twenty
First Amendment Effective Date (as defined in Section 13 of this Amendment and
after giving effect thereto) (it being understood and agreed that any
representation or warranty which by its terms is made as of a specified date
shall be required to be true and correct in all material respects only as of
such specified date) and (ii) there exists no Default or Event of Default on the
Twenty First Amendment Effective Date after giving effect to this Amendment and
Waiver.

         10. This Amendment and Waiver is limited as specified and shall not
constitute a modification, acceptance or waiver of any other provision, except
the provisions specified above, of the Credit Agreement, the Pledge Agreement or
any other Credit Document.

         11. This Amendment may be executed in any number of counterparts and by
the different parties hereto on separate counterparts, each of which
counterparts when executed and delivered shall be an original, but all of which
shall together constitute one and the same instrument. A complete set of
counterparts shall be lodged with the Borrower, the Agent and each Lender.

         12. THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAW OF THE
STATE OF NEW YORK.

         13. This Amendment shall become effective on the date (the "Twenty
First Amendment Effective Date") when (i) the Borrower and the Required Lenders
shall have signed a counterpart hereof (whether the same or different
counterparts) and shall have delivered (including by way of facsimile
transmission) the same to White & Case LLP at 1155 Avenue of the Americas, New
York, New York 10036 and (ii) the Payments Administrator receives a fee equal to
$125,000 for pro rata distribution among the Lenders according to their
respective Commitments under the Credit Agreement. This Amendment shall become
void and be of no force and effect on the 12th Business Day after the Twenty
First Amendment Effective Date unless, prior to such date, G&G or Ghaznavi
Canada Inc. pledges an additional 1,000,000 shares




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of Consumers Stock (as such term is defined in the Pledge Agreement) pursuant to
Section 4.1 of the Pledge Agreement.

         14. From and after the Twenty First Amendment Effective Date, all
references in the Credit Agreement and each of the Credit Documents to the
Credit Agreement shall be deemed to be references to the Credit Agreement as
amended hereby.


                                      * * *






















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         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this Amendment to be duly executed and delivered as of the date first above
written.


                                       ANCHOR GLASS CONTAINER CORPORATION


                                       By /s/ M. William Lightner
                                       ----------------------------------
                                       Name:  M. William Lighter
                                       Title: Chief Financial Officer


                                       BT COMMERCIAL CORPORATION


                                       By
                                       ----------------------------------
                                       Name:
                                       Title:


                                       PNC BANK, NATIONAL ASSOCIATION,
                                          Individually, as Co-Syndication
                                          Agent and Issuing Bank


                                       By /s/ Enrico Della Corna
                                       ----------------------------------
                                       Name:  Enrico Della Corna
                                       Title: Vice President


                                       BANKERS TRUST COMPANY


                                       By
                                       ----------------------------------
                                       Name:
                                       Title:




<PAGE>   7


                                       THE CIT GROUP/BUSINESS CREDIT, INC.


                                       By /s/ Karen Hoffman
                                       ----------------------------------
                                       Name:  Karen Hoffman
                                       Title: Vice President


                                       FIRST UNION NATIONAL BANK


                                       By /s/ Anne D. Brehony
                                       ----------------------------------
                                       Name:  Anne D. Brehony
                                       Title: Director


                                       FLEET BANK


                                       By /s/ Cynthia G. Stannard
                                       ----------------------------------
                                       Name:  Cynthia G. Stannard
                                       Title: Vice President


                                       KEY CORPORATE CAPITAL, INC.


                                       By
                                       ----------------------------------
                                       Name:
                                       Title:


                                       MELLON BANK, N.A.


                                       By
                                       ----------------------------------
                                       Name:
                                       Title:




<PAGE>   8


                                      NATIONAL BANK OF CANADA


                                      By /s/ Donald P. Haddad
                                      --------------------------------------
                                      Name:  Donald P. Haddad
                                      Title: Vice President/Manager


                                      By /s/ Gerald B. Knell
                                      --------------------------------------
                                      Name:  Gerald B. Knell
                                      Title: Vice President


                                      NATIONAL CITY COMMERCIAL FINANCE, INC.


                                      By /s/ Gregory A. Godec
                                      --------------------------------------
                                      Name:  Gregory A. Godec
                                      Title: Senior Vice President


                                      SUMMIT COMMERCIAL/GIBRALTAR CORP.


                                      By /s/ Jay Oliner
                                      --------------------------------------
                                      Name:  Jay Oliner
                                      Title: Vice President