Of the expensive variety, like others listed:
Camelback Elixir tablets can be had for less than Nuun if you look around, good product.
Hammer Nutrition makes a product called Endurolytes Fizz, it's their electrolyte tablet similar to the above products.... excellent supplement. I've used them in the past for 100F runs after work, help ward off cramps, excessive salt loss, all that stuff associated with being active in the desert during April-Oct. Highly recommended.
However, the liquid gold of trail drinks for adding spice to your Aquamira tainted water is Kool-Aid Tropical Punch in the single serve powder packs (makes 2quarts... really sweet... or 1L just right), those are cheap cheap and there is a Sugar-Free version. Just watch your clothing, this stuff stains everything. Those can be acquired anywhere.