I make these smoothies for the boys almost every single day, either as part of their breakfast or a quick after school snack. I'm always worried about Brody's calcium intake, so I tend to add calcium powder to just about everything. Ditto flax seed for a good source of Omega-3 fatty acids. Feel free to leave those ingredients out if you don't need/want them.
1-1 1/2 cups frozen berries (strawberries, blueberries, raspberries, etc.)
1/2 tsp flax seed meal
1 tsp calcium powder
1-1 1/2 cups apple juice
Combine in blender. Adjust amounts of berries and juice until desired consistency. Enjoy!