I have the solution because I too have been in this exact situation, but you can't eat much or you'll be extremely uncomfortable.
The day before you go, drink a full bottle of magnesium citrate. This will cause liquid diarrhea and completely empty you out. This is used before Colonoscopies to give the doctor a clear view.
Then for the next 3 days eat very little while taking 3 immodium each day.