Drain the pineapple, reserving the juice. Add enough water to the juice to make 1 cup. Combine the juice and water mixture with the cranberries and sugar in a saucepan. Bring to a boil and let gently boil, stirring occasionally, for 10 minutes or until the cranberries start to pop. Stir in the pineapple.

Pour into a serving dish and let cool. Cover with plastic wrap and refrigerate for 4 hours or up to 2 days.