in a small freezer bag, add together an assortment of frozen fruit, freeze. also freeze one serving of yogurt. when you want a smoothie, mix the frozen fruit and yogurt in a blender with 1 cup 100% fruit juice.
for fruit I take one handful each strawberries and blueberries, then one half of a chopped banana. I use plain yogurt, add orange juice and this tastes awesome! yummy and healthy!
alternative: fat free yogurt, add spinach instead of blueberries, add sweetener to taste if it turns out bitter