Magnesium sulfate / potassium sulfate / sodium sulfate
"I've had several colonoscopies. Previous prep was always basically Miralax/Gatorade plus one or two other laxatives.  Suprep is better by far.  Less to drink, less bloating. Two dose regimen meant that I got a decent night's sleep because the evening purge slowed to a stop before bedtime.  Didn't taste that bad, like salty fruit punch.  I'm actually not dreading the next colonoscopy."