Add 4 cups of water to a medium saucepan and bring it to a boil over medium-high heat.
Once boiling, add 1 cup dried hibiscus flowers and turn off the heat immediately.
Let the hibiscus steep in the hot water for 10 to 15 minutes until the liquid turns deep red.
Pour the mixture through a fine mesh strainer into a large pitcher, removing all the solids.
Add ½ to ¾ cup sugar to the warm liquid and stir until fully dissolved.
Add 2 to 3 cups cold water to adjust strength. Stir in 1 to 2 tablespoons fresh lime juice if using.
Refrigerate until cold or serve immediately over ice.
