Crush pineapple pieces *very* finely. Put together with the pineapple juice in a pan, add the sugar. Leave to stand over night. Drain syrup and strain pineapple pieces through a cheese cloth or in a food processor. Mix juice with rum and vodka, add lemon juice to taste. Pour in a 0.7 l bottle and fill to the brim with pineapple juice or water. Leave at least one week.