After a workout, I fill the bottle with cold water and then add a packet of this energy booster. Besides vitamin C, it contains 7 mineral ascorbates, 32 mineral complexes and B vitamins. The calories per packet is only 25. (I buy the Walgreen's brand which is less pricey than the similar Emergen-C product).
The packets are sold in a box of 36. I can't remember the cost, but it's quite reasonable.
Honestly, what motivates me to mix the cranberry or orange flavored powder in my water is that it's much easier to drink than plain old water. Even when I've sweat a lot, I don't get very thirsty so I have force myself to rehydrate. Obviously, if the water tastes good, I'll drink more.
After sweating and grunting and groaning, you and I know drinking water is a must. My equation for successful hydration assures I'm replenished and refreshed once I've drained every drop. You may want to try it too.