Simple, unadorned berries can help slim down a strawberry daiquiri. Start with 1 cup of no-sugar-added berries, either fresh or frozen. You get intense berry flavor for just 50 calories, compared with 255 calories in berries frozen with syrup. Add rum, ice, and sweeten the deal with 1 teaspoon of stevia, a sugar substitute. Blend into a slim and delicious frozen concoction.