Preheat the oven to 350 degrees F.
Line the inside bottom of your cheesecake pan with parchment paper. To do this easily, flip the pan upside down and trace a circle on a piece of parchment with a pencil. Cut along the outside of the traced circle and place the finished circle at the bottom of your pan. Grease the sides of the springform pan. And set aside until ready to use. In a large bowl, prepare the cake batter according to the box directions. Then, spoon the batter into your prepared pan, being sure to scrape out the bowl with a rubber spatula to get as much of the batter as possible. Place the pan in the oven and bake for 18-20 minutes(or according to the box bake time) or until a toothpick comes out clean. Remove the baked cake from the oven and allow it to cool for 15 minutes or until it is cool enough to handle.
Then, using the bottom of a glass jar or cup, squish the cake down to about half its previous volume. This will help create a more crust-like texture and make more room for your cheesecake.
Place a large piece of foil over the bottom of the cheesecake pan. (It should cover about 2/3 of the outside sides of the pan as well) and set aside until ready to use. In a large bowl, combine the softened cream cheese, sour cream, sugar, and vanilla extract. Beat with an electric mixer at high speed until the mixture is smooth and creamy, and there are no lumps of cream cheese. Scrape down the sides of the bowl and mix again. Add the eggs and beat the mixture on medium speed until completely combined. Then add the rainbow sprinkles and fold to combine with a rubber spatula. Spoon the finished cheesecake mixture onto your cake crust; the mixture should fill the pan to the top, but you might end up with a little extra filling. Smooth out the top of your cheesecake with your spatula. Place the cheesecake in your water bath pan of choice and fill it with 2-3 inches of water.
Bake for 1 hour. At this point center should be set, but still jiggly. If your cheesecake isn’t quite set, though, bake for an additional 15-20 minutes or until the center is set.
Once the center of the cheesecake is set, turn off the oven and leave the door closed for 30 minutes. The cheesecake will continue to cook, but begin to cool slowly as well.
Finally, crack your oven door, and let your cheesecake sit in the oven for an additional 30 minutes. Before removing it from the oven and water bath.
Place your cheesecake in the fridge and allow it to chill for 4-6 hours or overnight.
Once the cheesecake has chilled, run a knife along the sides of the pan to help make sure the cake doesn’t stick to the pan. Then release the springform pan, and transfer the cheesecake to a plate(though you can also serve it from the bottom of the pan).
Dollop the top of the cheesecake with whipped cream and rainbow sprinkles. You can also top the individual slices after cutting the cheesecake if that works better for you! Cut into 12 slices and serve.
Enjoy!