albertagirl,
I don't think I ever had that prep with the J Pouch but I did when I had my colon. My pouchoscopy prep was what kjeane described, fasting and enemas. No oral laxatives. Did you confirm with them that you have a J Pouch? Because one year I was given the wrong prep instructions by someone who thought I was a coloned patient.
Assuming this instruction is correct, I hope you can get most of it down, just try to drink it rapidly and don't think about the taste of it. Because when you start to think about and imagine the taste of the next gulp it becomes even more vile in taste. Just pretend that it is water and that you are thirsty and think positive thoughts. Good luck and let us know how much you got down.
By the ways it will give you an explosive diarrhea and I think your concerns about dehydration are valid.