The standard flavors are tamarindo (made with tamarind), horchata (rice and cinnamon), and jamaica (hibiscus), but you can make agua fresca — a cooling, refreshing drink — from almost any juicy fruit.
Watermelon Agua Fresca With Strawberry
They were selling this combination — watermelon and strawberry — agua fresca at Whole Foods today. The samples were so good I had to make this watermelon drink recipe for myself when I got home. I think they would freeze well, too, as a fruit popsicle (without the added water, and maybe a bit more sugar).