I was on the 2 day fast. Clear liquids the first day and the half-lytlely the next. I honestly could only get two glasses down. It made my stomach cramp horribly. I was cramped and using the bathroom ALL DAY! I also had to drink that Fleets' Oral Phosphate soda which is pretty much as bad as the Half-Lytely. Anyway, my colonoscopy was scheduled for the next morning. The night before, I was so sick of going to the bathroom and felt so incredibly ill that i didn't care if i finished all of the liquid. The doctor said, after the procedure, "wow, you must have finished every last drop because you were really cleaned out!" I just nodded. Honestly, if you are on a clear liquid diet for 2 days and drinking as much of that crap as you can, i wouldn't worry too much about
finishing it. There was no way in hell i could!
Also, try Dulcolax pills. Take 4 of them and that'll clean you out!