For the plum rum cocktail, squeeze limes and mix with sugar and white rum. Wash the plums, cut them in half and remove the seeds.
Cut the flesh into thick slices and marinate together in the rum-lime mixture – at least 30 minutes.
Now pour 1/4 of each of the prepared rum plums into a long drink glass, add a sprig of mint and four ice cubes and top up the plum-rum cocktail with mineral water, depending on the desired alcohol intensity.