Add the dried mint and hibiscus flowers to a tea strainer and steep in cold water overnight or for at least 8 hours. If you don't have a tea strainer you can steep the herbs directly in the water and strain with a sieve.
After done steeping, remove the tea strainer, add the sugar, and shake until dissolved. Cool in the fridge and serve with plenty of ice.
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Notes
Goes great with vodka or rum for a summer cocktail!