In a blender or food processor, purée cabbage, cucumber, and water. Add frozen blueberries, frozen banana, and vanilla yogurt. Purée again until smooth. Garnish with fresh blueberries.
To add more sweetness and a creamier texture, use an additional frozen banana.
Per serving: 131 calories, 1 gram fat (0.5 gram saturated fat), 3 milligrams cholesterol, 38 milligrams sodium, 29 grams total carbohydrates, 4 grams fiber, 4 grams protein.