I had a half century round trip commute at the time of my colonoscopy. I loaded the pannier with Gatorade and Mountain Dew for the day--enough sugar calories to power the biking plus no chance of dehydrating. The riding went just fine. Of more concern was that I needed to take a laxative pill at work that was supposed to kick in in about four hours. The commute home was two, and I was sure counting on the accuracy of that four hours... At home, the fun really began with a bottle of Mirilax in half a gallon of Gatorade to get the show really moving...
I'm working from home these days so next year's won't have all that pre-prep excitement.