How to Make It
Remove the peel from grapefruit using a vegetable peeler, making sure to leave as much pith (the white part) on the grapefruit and not on the peel as possible. Cut peel into 1/4-inch-wide strips.
Bring granulated sugar and water to a simmer in a small saucepan over medium, stirring occasionally to dissolve sugar. Add peel strips, and cook 5 minutes. Remove pan from heat; pour mixture into a small bowl, and cool to room temperature, about 1 hour.
Pour mixture through a strainer over a bowl, reserving grapefruit syrup in bowl for use in cheesecake. Gently pat excess moisture from peel strips. Toss in sanding sugar; arrange in a single layer on a wire rack, and let stand until completely dry, about 24 hours.