Peel and quarter the pineapple, cut out the hard core and cut the flesh into small cubes. Put the rock candy in a mason jar and pour the grain over it.
Strain after about 10-14 days and fill the liqueur into bottles.
The amount of sugar always depends on the sweetness of the pineapple, sometimes you only have to add 100 g. Just taste it after a week, you can still add sugar.