I agree with the BRATY diet:
* Bananas
* Rice/simple cereal
* Applesauce...not apple slices...unsweetened applesauce, maybe even diluted if that's easier on him.
* Toast
* Yogurt
Yogurt (plain, maybe with a little applesauce added) would be the ONLY diary I would consider...if you use the sweetened yogurts...you're defeating the purpose of the simple, natural cultures which is what will help nip diarrhea in the bud.
Also, if you use Gatorade, you MUST dilute it...one part Gatorade to one part water...little bodies REALLY can't handle the sodium content at full-strength so it's important to go half-and half. I have also found that if I use the "Rain" varieties...they have WAY less dye in them. My feeling is: if their little body is already struggling with some kind of bug...the last thing they need is a bunch of unnecessary chemicals poured in there too.
My son wouldn't take Pedialyte in the drink version but he happily drank the frozen "pop-ice" style pedialyte so that might work for you too.
Best of luck and hang in there!!! Sometimes it's way harder on Mom than the little one when a kiddo is sick so understand you're not alone ;)
Good Luck!!!