Sprinkle cake mix evenly over top of fruit. Tip: Gently massage the cake mix while still in the bag to break up any lumps.
Pour 2 cups Sprite evenly over top of cake mix to cover. Tilt pan back and forth to help cover the dry cake mix. Add more Sprite (½ cup or more) if you notice some dry spots. Adding too much Sprite may create too much liquid on the bottom so be aware of that.
Bake for 45 minutes or until the berries are cooked and the top is browned. Let cool about 5 minutes before serving. Top with vanilla ice cream, if desired.