I have had lots of colonoscopies over the years and because I have had so many parts of my digestive tract removed due to crohn's flares/strictures. I can't tolerate the large quantities they like you to consume. So what helps me is that if I know that I will be doing a prep I start days before the cleansing, I eat as little or no solids. So I end up having to drink less of the nasty coctail thay prescribe. I have even asks the Dr's if the colon was clean enough to get a good look and they said it was fine, hope this helps.
I just had a colo/endo the other day and did a lot of research on how to make the prep more tolerable. I combined a lot of ideas and it worked out fine for me so I wanted to share.
I did the fleet phospho-soda, cut 1 1.5 oz bottle with 4 oz. of WHITE grape juice. I kept the fleet and grape juice in the fridge for hours prior to drinking so it was cold. I also kept a glass of fresca next to the phospho/juice conconction. The sweetness of the juice counteracts the saltiness of the sodium phosphate IF YOU DRINK IT QUICKLY. I held my nose and drank it down as fast as I could. In between I would take a sip of the fresca. Once I finished it I took a hard jolly rancher lemon candy and sucked on it until the flavor of sodium phosphate could no longer be tasted.