Wash the grapes and prick several times with a darning needle. Place in an earthenware vessel. Dissolve the sugar in the water and pour over the grapes. Now fill the earthenware vessel with grappa until all the grapes in the grape brandy have disappeared.
Seal the jar airtight with preserving foil and refrigerate for two weeks.
Tip: This high-proof dessert can be served with ice cream, but the grappa grapes are also very tasty when consumed on their own.