Quarter the apple and slice out the seeds and core. Roughly chop the apple and add it to a blender. Peel and break in the banana.
Slice the skin and white pith off the ruby grapefruit, then slice the segments out of the membrane with a small sharp knife. Add the grapefruit to the blender and squeeze in any juice from any scraps of grapefruit clinging to the skin.
Tuck in the baby leaf spinach. Add a few ice cubes and pour in 300ml maple water. Blitz for a few mins till smooth and combined, then serve.