Yes, AC Marriott provides free breakfast to their customer for the period they stay. But, there are certain groups who get this service. If you are not among them, then you might not receive the free breakfast from their side. Though there are some offers and coupons through which one can easily get it even if they are not belonging to their specific category.
Now, in the specific group, like platinum, Titanium, Ambassador Status members are coming in this group. These all the premium groups of the hotel that provide many other services too and that without any cost. One can purchase these program and leverage this, but it has more benefits when the person uses the same hotel chain or travel quite frequently. Everyone can use this and get the benefits like free breakfast. So now you can see how easily you can get the free food from the AC Marriott, if you have received any coupon or something, then don’t forget to interact with them and let them know about it, so you can too enjoy it, without having access to the premium members list.