I'm not part of the challenge since I drink loads of water normally (at least a gallon a day) but wanted to share something that makes the water better for me nutritionally and taste-wise. I juice about 3-4 lemons and add to a gallon of water a day. I don't add sugar (lemons naturally have a small amount of sugar) nor do I use bottled lemon juice. The lemon juice adds an AMAZING amount of minerals and vitamins (especially B!!!) in addition to hydration, and tastes great. I always drink it through a straw.
Not sure if this was mentioned but I hope it helps. I typically don't drink anything else, other than unsweetened tea (hot or cold) with cinnamon on the occasion. If you're accustomed to drinking sugary drinks it may taste odd at first. But once you get into the habit of drinking your water with lemon, and you go back to plain water, it'll taste weird and empty...lol
(Limes are good too!)