Preheat the oven to 350°. Prepare three 9 inch round baking pans with nonstick cooking spray. In a large bowl, beat together the cake mix, milk, oil, eggs, vanilla pudding mix, and orange gelatin mix until well blended, about 2 minutes.
Divide the cake mix evenly between the three prepared baking pans. Bake for approximately 25 minutes or until a toothpick inserted in the middle returns clean. Allow the cakes to cool in the pans on a wire rack for 10 minutes before removing the cakes to continue cooling on the wire racks.
Meanwhile, in another large bowl, stir together the pineapple, sugar, coconut, and sour cream. Remove one cup of the mixture and set aside for the frosting.
When the cakes are cooled, place the first layer of the cake onto a flat plate or serving dish. Add half of the remaining filling, spreading evenly. Add the second layer of cake and top with the remaining filling.
Place the final layer of cake on top. Stir the thawed whipped topping into the reserved 1 cup of filling. Use this mixture as a frosting and spread over the cake on the top and sides until completely covered and even.
Refrigerate the cake until ready to serve.Prior to serving, garnish with sliced oranges and pineapple tidbits.
Notes: because the frosting uses whipped topping in the icing, this cake should be refrigerated between servings.Homemade whipped topping is not recommended as it may separate. Make sure to drain the crushed pineapple very well, squeezing the pineapple against it’s fine mesh strainer to remove all of the liquid.