Always best to try a few things... here are some options:
* Gu Electrolyte Brew
* Hammer Heed
* Accelerade Hydro
* PowerBar electroyte sticks or endurance
* Camelbak Elixer (fizzy)
* Nuun (fizzy)
* Clif Shot Electrolyte
Also... maybe a dumb question, but are you drinking the bottled crap they sell in gas stations and grocery stores? Or are you drinking the powdered mix (or better yet... the endurance formula mix)? If you are using the pre-bottled stuff, it's just a sweet treat for kids. If you want something that will really perform you need to use the mixes.
Also, if your stomach is really fickle, you could always use the hammer endurolyte pills/powder (or any other electrolyte tablets, I know pacific health makes a good one too)