The flavoured ice rings can be prepared in advance. To help unmould the ice rings, soak the base of the doughnut pan in hot water. Using a pointy, non-metallic utensil (such as a wooden skewer), press between the ice and the edge of the pan to pop the ice rings out. Store the ice rings in an airtight container in the freezer. This way, they will be ready to go when you serve the punch.
These ice rings are also great in a glass of juice or sparkling water.