In The 17 Day Diet book, Dr. Moreno advises us to use the juice of half a lemon. You may decide it easier and more cost effective to use bottled lemon juice. Update in 2014: In the Breakthrough Edition, Dr. Moreno advises using an entire lemon.u003cbr/u003eIf you use lemon juice from a bottle, count on about 3-4 tablespoons of lemon juice per 8oz of water.