6 ounces frozen grapefruit juice concentrate, undiluted
6 ounces frozen pineapple juice concentrate, undiluted
2 ½ cups water
1 teaspoon honey or maple syrup
4 ice cubes
2 tablespoons lime juice
Whirl all ingredients together in a blender until frothy. Serve at once in long stemmed glasses with a thin slice of lime on the rim of each glass.