For a sugar-free electrolyte replacement, I use Zenergize Hydrate.
Unfortunately it's much harder to find than Nuun. Their website suggests that they've given up on retail and are selling only through the web at this point. But it has no artificial sweeteners, no sugar alcohols, and no antifreeze ... worth bypassing the local stores, in my book, which I really try not to do. (Also, the tablets are larger; you'd have to break them in half for a bike-sized water bottle.)
Vitalyte looks really good as a sports drink, I hadn't seen that before. I've been using HEED - the xylitol isn't really that big of a concern for me, I just mentioned sugar alcohols in connection with Nuun since I know they do give some people trouble - but it looks like Vitalyte is both purer and less expensive, and I'm really not convinced of the need for long-chain carbohydrates during exertion, especially in drink form when you're ingesting it pretty much continuously.
Speed comes from what you put behind you. - Judi Ketteler