I got Nuun recently and loved it on my first ride (66 miles). Then I used it on a 75 mile ride and it didn't sit so well. I think it was just the slight amount of fizziness that my stomach didn't like (I never drink anything carbonated so am not used to that). After the first 50 miles my stomach felt too gassy to keep drinking enough and I got a bit dehydrated. The 2nd day of the NEC 150 ride, I drank watered down Gatorade and that worked fine. But my hydration hose grew mold a few days later, so the sugar was a bad thing.