I like Accelerade fruit punch, watered down a little. And those Nuun tablets were really great a couple years ago on a tour with 3 consecutive days of 104 degree heat and 60-80 mile/day. I found that eating real food and drinking water with Nuun tablets did the trick and helped avoid upset tummy.
Does anyone use a product called Fizz? I don't know how they spell it. It is supposed to be a nutrition drink with a little more to it...more like a liquid meal for really long events, like Ironman, etc.
I really struggle with upset stomach on long strenuous rides, and it doesn't seem to matter which products/foods.
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury