1. Cut the watermelon into roughly 1-inch cubes (precision is not important) and remove the seeds. If you're using other fruits, prepare them accordingly, removing seeds or skins and cutting into small pieces if necessary.

2. Combine all ingredients and blend in blender or food processor until smooth.

3. Pour through a strainer into a pitcher, forcing through most of the pulp. (The pulp is tasty and adds texture to the drink, but if you must have a clear drink, use a fine strainer and don't force the solids through.) Chill and serve.

CONCENTRATION: If you like agua fresca enough that you decide to keep a pitcher in the fridge, you'll soon notice that a big pitcher takes up a lot of room. Fortunately, it's easy to make it in a concentrated form that you can mix with water when you're in the mood for a glass. Put about 4 cups of fruit in a tall, narrow pitcher, add the sugar and lime juice, and then pour in just a little water, only enough to fill the spaces around the fruit (maybe 1 cup). Buzz it with the blender and put the result in the refrigerator to chill. When you want a tall glass, pour in a little of this thick slurry, then stir in three parts water to one of fruit, and add ice cubes.

Plan to drink it soon - it seems likely that the fruit would oxidize, ferment, or otherwise deterioriate after a few days in the fridge. But I'm not sure ... I've never let it last that long.

MATCHING WINE:
If you want an alcoholic version of agua fresca, you can add a shot of Tequila. Harden advises against it, though: "Uh-uh! Messes up both drinks. If the tequila is good enough to drink, don't mix it, drink it separately, then enjoy the agua fresca afterwards."