1. Crush pineapple pieces very finely and add, with the sugar, to pineapple juice in a pan. Leave to stand overnight.
2. Drain syrup and strain pineapple pieces through a cheese cloth or in a food processor. Mix juice with rum and vodka, and add lemon juice to taste. Pour into a 0.7 litre bottle and fill with pineapple juice or water. Leave for one week.