Pour in the cold water, and if you like, add a few sprigs of fresh mint for an extra burst of freshness. Refrigerate the mixture for at least an hour before serving. For the best taste, enjoy it within 24 hours, although it can be stored for up to 3 days in the fridge. When ready to serve, you can include lemon slices for a citrusy twist or add a splash of sparkling water for a fizzy touch.