The purpose of the glycerin in the L-Drink is to provide the body with an alternate energy source to use instead of lean body mass during days 2-5 of the fast. So, the L-Drink helps protect your lean body mass while keeping you in a fasting state. You will use the amount of L-Drink associated with your weight and mix is in with water in a large water bottle (32 oz). The weight on the L-drink is marked from top to bottom, not from bottom to top, meaning the more you weigh the more L-drink you will have to pour.
If you do not wish to use the L-Drink, skipping it should not interfere with any rejuvenation effects, but it may impact your overall experience and energy level on the meal program, and put at slightly higher risk of losing muscle mass during the program. The L-Drink is intended to be consumed during the diet as a 1-time use only.