100oz of water is not anywhere remotely near anything that would constitute "water intoxication". It is a very well studied and known standard that for optimal health people should drink half their body weght in oz of H2O. Do a little research into "The Water Cure" I believe that there is a forum for it here on Curezone
Many people that do the Master Cleanse which is not water fasting and technically a mono fast will drink a gallon or water a day in addition to the 60 to 120 oz of lemonade on a regular basis. The main deal is that when one is fasting it helps keep the toxins moving out of the system. Personally I can't do that much and function in my everyday activities cause I would be peeing constantly but I will easily consume 60 to 90 oz in addition to my 60 to 90 oz of lemonade daily. I have done 10+ 40 day fasts over the last 6-7 years with exemplenary results.