I gotta share this recipe. It's for a mint-flavored syrup that you dilute with cold water. I've made this every summer for several years now, and it sounds weird but is *great*, especially in very hot weather. The recipe is copyrighted (not by me, natch) and available on the web, so I'm just posting a link.
Use a big handful of mint.
Use a good white wine vinegar, as it's a major ingredient.
Once you have the syrup, put a shot or two of it into a big glass, add a big handful of ice, fill the glass with cold water, and stir. You may have to experiment a bit to work out what strength you like.