Magnesium sulfate / potassium sulfate / sodium sulfate
"Like many, I dreaded the prep for a colonoscopy as I typically have a gag reflex. However, I did my research (read every review on here) and came up with a plan that worked really well. Here's the poop (pun intended): About 3  have a light bland supper. Two days before, eat bland soft food (plain scrambled eggs, smooth yogurt, etc) and drink lots of water and/or clear liquids. Day 1 prep: eat 2 plain scrambled eggs for breakfast and then drink lots of clear non-acid liquids. Buy some Crystal Light Powder and make a strong pitcher. Put in fridge a few hours before first dose. Add to Suprep 30 min before taking and put in fridge. Cut a lemon wedge and hold under your nose, drink through a straw. It's bearable and it works well."