Combine the hibiscus flowers, sugar, and water in a medium saucepan over medium heat and cook for 30 minutes, stirring occasionally, until the syrup coats the back of a spoon.
Strain through a fine-mesh sieve, and pour the liquid back into the pot. Bring to a boil and simmer over medium-low heat until the liquid is reduced to the consistency of a thick syrup, about 20 minutes. Cool to room temperature and store refrigerated in a glass or plastic container.
