Drain juice from pineapple into a measuring cup. Fill the measuring cup with enough water to equal 1 cup liquid total.

Stir pineapple juice mixture and sugar together in a saucepan; bring to a boil, stirring constantly. Add cranberries and return to a boil. Reduce heat to low and simmer until cranberries burst, about 10 minutes.

Mix pineapple chunks into cranberry mixture. Cool to room temperature before serving.