I like coconut water. Tastes good to me, and it does have good potassium content. It's pretty expensive though, and I consider it a luxury post ride treat. I can burn through 3 or 4 liters of fluids in the summertime pretty easily. I mostly use good old ERG/Gookinaid/Vitalyte on the ride. I make it fairly weak. If I bring two bottles typically one is plain water and one is electrolyte. Sometimes I do diluted orange juice. It has nearly as much potassium as coconut water, and I usually have some in my fridge. It has more sugar, but diluted less than 50% seems to bring it down to a digestible level.