Ultima Replenisher -- no sucrose, no fructose, no HFCS. I've been using it since 2009, and I wouldn't drink any other product.
I tried to find out more about this product. All I could find was that it contains maltodextrin, which of course is a long chain glucose sugar, i.e. the "no sugar" is BS. However, as far as I can tell, they want you to use so little of it, just a few grams/bottle, that it's pretty much zero in the nutrition department. It does have electolytes.