Agree with Mr.W about DIY drinks - 50/50 water/juice and a pinch of salt is absolutely fine, and I take this if I'm carrying a bottle and running 1-2 hours. I use Nuun tablets if I'm running 2-3 hours off-road - they're easy to pop in your bladder pack and don't make it too disgusting to clean. As for carbs on the go, the SiS gels are brilliant - not too sweet, and give you a real boost. Apparently the caffeinated ones are like rocket fuel, but having dodgy guts at the best of times, I haven't been tempted!