Forward osmosis is an interesting concept, but I was not impressed by the amount of water they provided - something like half a liter per capsule, and that over a very long period. In any situation where you are doing even moderate work, that amount of water is minuscule. For most applications, it would be much simpler merely to pack the water in the first place.

I have had good experience with sports drinks for rehydration, although I usually dilute Gatorade about fifty-fifty with water. It is better that way when working hard.