Put all ingredients, except the yeast, in a saucepan, bring to the boil and let it boil several times. Let it steep for a day.
Pour through a sieve, warm to body temperature and dissolve the fresh yeast in the tea drink. Fill into glass bottles, cover the opening with a cloth and let rest for two days in a place not too cool.
Filter through a cloth to remove impurities.
Serve with ice cubes. If you like, you can mix it into a rum cocktail.
Sorrel is a tropical hibiscus plant. Alternatively, you can use the dried hibiscus flowers from other countries.