Agua de Jamaica (Hibiscus Flower Cooler — Mexico)

4 cups water
1 cup dried hibiscus flowers (1 1/2 ounces)
1/3 cup granulated sugar, or to taste
2 cups ice

In a saucepan, bring water to a boil and add flowers. Simmer mixture 5 minutes and remove pan from heat. Let mixture stand 30 minutes to infuse. Pour infusion through a sieve into a glass pitcher, pressing on solids, and discard flowers. Add sugar and ice, stirring until sugar is dissolved. Chill cooler and stir before serving.