All you need is a package of basil, or a few leaves from a plant: crush them between your fingers to release the fragrance and oils, and let it infuse a bottle of lemonade, or a pitcher of same, in the fridge. Tarragon and rosemary also make a tasty drink.
If you lack the patience or aren’t partial to the tartness of fresh squeezed lemonade, I’ve found that the Santa Cruz Organic that Whole Foods sells for $1/32 fl. oz. is tastier than, say, Country Time, which is pretty bland and overly sweet.