1 Rinse apple, wipe dry, cut into quarters and chop coarsely, including the seeds.
2 Rinse the currants and drain in a sieve. Reserve 1 stem with fruit for garnish and strip the rest of the currants from the stems.
3 Squeeze out grapefruit juice.
4 Combine apple cubes and stripped currants in a juicer and extract the juice.
5 Pour into a tall serving glass filled with ice cubes and stir in the grapefruit juice. Top with mineral water, garnish with reserved currants and serve immediately.