To make Grapefruit Cinnamon Shrub: 1 cup grapefruit segments (add peel for extra flavor), 1 cup sugar and 1 cup apple cider vinegar. In a mason jar, first muddle sugar with grapefruit peel to release the peel oils. Add grapefruit segments and muddle to extract juice. Finally stir in the apple cider vinegar, add a cinnamon stick and let sit in fridge for 2-4 days for flavor to develop. Strain and keep liquid in the fridge.