Add the grapefruit segments to a blender, making sure to remove any seeds and excess membrane for a smoother texture.
Add the coconut water, frozen pineapple, baby spinach, frozen banana, lemon juice, ginger, and honey (if using) to the blender.
Toss in the ice cubes and blend on high speed for 1–2 minutes, or until completely smooth.
Pause to scrape down the sides of the blender as needed to ensure everything is well incorporated.
Taste and adjust sweetness by adding a little more honey, if desired.
Pour into a tall glass and enjoy immediately while cold and refreshing.