It's a low/no carb variety and just a pretty generic raspberry lemonade sort of flavor. Nothing to write home about.

EDIT: In general, it's all basically just soda or diet soda with extra caffeine. You can probably find a diet drink mix like MIO or Crystal Lite that tastes the same without the cost and hype, just less caffeine. I'll drink 'em sometimes if I want a little pick me up and I'm not feeling a coffee, but I won't go out of my way for one because of the flavor.