Preheat the oven to 350 degrees F. Spray a 9x13-inch baking dish with non-stick cooking spray. Set aside.
In a large bowl, mix together the white cake mix, water, oil, eggs, and vanilla. Beat on medium speed for 2 minutes. Pour cake batter into greased 9x13-inch baking dish.
Bake for 26-32 minutes, until a toothpick inserted into the center comes out clean.
Remove from the oven and immediately poke holes in the cake using the end of a wooden spoon or a wooden skewer.
In a medium bowl, combine the boiling water and Jello mix. Stir until the gelatin is completely dissolved. Add in the Crush soda and stir well.
Slowly pour the Jello mixture all over the top of the cake, making sure the mixture gets down in all the holes. Cover and refrigerate 1-2 hours.
Spread Cool Whip on top of the cake. Add sprinkles, if desired. Refrigerate at least 2 hours before serving. Garnish with drained mandarin oranges at serving time.