Place the hibiscus flowers in a (1-quart) jar or medium pitcher. Add the water, stir to combine, and chill until bright red, at least 20 minutes. For a deeper color and flavor, chill overnight.

Pour the tea through a fine mesh strainer set over a bowl or pitcher to remove the hibiscus flowers. Pour into glasses filled with ice and sweeten to taste, if desired.

Garnish with fresh mint and raspberries.