Smoothies!
My new favorite cool drink is the Mango Passion Fruit Smoothie from Dunkin Donuts. They are made with real fruit and yogurt, and are a good source of Calcium and Vitamin C (especially helpful now that I'm eating and drinking for 2!).
What's even better is that there are coupons for FREE 16 oz. smoothies in the September issues of Parents and child magazines (that's how I tried it in the first place).