I drink plain water. I have tried various carbohydrate/isotonic powders on long rides in the past but I've realised that I don't need them and I cant feel/see any benefit or better times/results from using them. I've had some gastric and other health problems recently so its best for me to avoid anything that risks me feeling sick or bloated anyway, and odd though it might seem, I actually prefer the taste of water! I used plain water on the past few 200km rides I did, and even in the Alps in July I used very few sports/isotonic drinks. I only ever used carbohydrate powders to supplement some intake of 'real' food on rides though. If you rely totally on drinks for your fuel on rides, you may need to replace the KCals from the drinks with KCals from solid food or gels if you're going to try riding without. The only powders I'm interested in trying/using are those which do not contain any KCals (in the form of carbohydrates) but are hypertonic - containing only electrolyte salts. I'd be interested to see if I drink any less water on hot rides when using them. Will have to wait till summer holidays to find out though!