One of the simplest and healthiest refreshingly cool beverage is a homemade smoothie.
Add 2 cups of frozen organic blueberries, 1 organic banana, and 1/2 cup of milk (I prefer non-dairy soy due to the protein and nutrients) and blend together.
You can always add organic protein powder as an option.
This is a wonderful after school treat especially during the summer for my son and his friends when they come to play.