Since we only do day hikes when we travel, we typically pick up several bottles of PowerAde Zero and do a roughly 50/50 mix of this with water in our Camelbaks. It adds a bit of flavor and also helps restore electrolytes and some vitamins. It's getting to be a bit harder to find, though (for example, on our way from SFO to Yosemite, our usual stops seem more and more only to carry GatorAde (which my wife doesn't like) or the full-sugar version of PowerAde (which I don't like).
I'm curious if anyone else bothers with any kind of water "fortification" like this. If you're backpacking, I'm sure that, at most, you'd add some kind of powder or tablets to your water (as opposed to the absurdity of carting bottles of PowerAde or GatorAde with you) but how many of you even bother with that? For anyone who DOES use water additives, what brands do you like? (I know PowerAde themselves make a powder (which I've only ever seen available via mail-order) but it's typically much more expensive to buy a small packet of powder than a large bottle of the mixed drink).