01 - Combine the orange, grapefruit, lemon, and banana in a blender.
02 - Add coconut water (or plain water) and ice cubes (if using).
03 - Blend on high speed until completely smooth.
04 - Taste, and add honey or agave syrup if additional sweetness is desired.
05 - Pour into glasses and serve immediately, garnished with a citrus slice if desired.