Pour a cup of liquid from the mandarin oranges into a microwavable bowl. Microwave liquid and bring to a boil.
Add the orange gelatin into the liquid and stir until dissolved.
Cool the gelatin mixture until just warm.
Place thawed cool whip into a mixing bowl, add vanilla pudding and whisk until well incorporated.
Add cooled gelatin mixture to pudding mixture and whisk to incorporate until no longer lumpy.
In a 3-quart serving bowl, place a tight layer of cubed sponge cake.
Add the orange mixture on top of the cake cubes.
Spread a thin layer of cool whip.
Next, add a layer of mandarin oranges.
Repeat the steps in the same order.
Place inside the fridge to set for at least 2 hours before serving.