You can find dried hibiscus in two forms - on the left, the loose petals shown and to the right, the whole calyces which I've previously used - and for this recipe, either can be used.
(Sourced from Mexican Cooking by Cecilia Hae-Jin Lee)
4 cups water
½ cup caster sugar
½ cup whole dried hibiscus flowers or ¼ cup loose hibiscus flowers
fresh lime juice, to taste
fresh mint leaves, to garnish
Place the water and sugar into a pot over a medium heat - stir until the sugar has dissolved and then allow the mixture to come to the boil. Once boiling, remove from the heat and stir in the dried hibiscus. Let it steep for 15 minutes, then strain - store in a glass container, seal and place in the fridge to cool completely.
When ready to serve, stir in freshly squeezed lime juice to taste and pour into a jug with lots of ice and sprigs of fresh mint.
If you're after a little bit of a kick, then try adding vodka or gin.