Makes 6 to 8 drinks
In a medium saucepan, add the grapes, lemon peels and sugar or coconut sugar and gently muddle. Add 1 cup of water and bring the mixture to a simmer over medium heat. Let cook, simmering, for 15 minutes.
Strain the syrup through a fine-mesh sieve over a bowl, discarding the solids. To serve, pour ½ cup of syrup into a glass and top with cold seltzer.