Combine apple, rhubarb, onion, apple juice, cranberries, honey and ginger in a medium saucepan. Cover and cook over medium heat, stirring occasionally, until the rhubarb is soft and the apple is tender but not mushy, 10 to 12 minutes.
Remove from the heat and let stand for 5 minutes.
Stir in vinegar. Remove the ginger; serve the sauce warm, at room temperature or chilled.