Add 1 cup cereal to 1 cup milk and let soak for 10 minutes. Strain and reserve milk.
Prepare a 9x13 cake pan with nonstick cooking spray (or grease and flour it). Preheat oven to 350°F.
In a mixing bowl, add cake mix, cinnamon, eggs, cereal milk, vanilla extract, and melted butter and mix until well incorporated.
Pour cake batter into prepared pan and bake in preheated oven as directed on cake box (approximately 27-28 minutes or until toothpick comes out clean).
Remove cake from oven and allow to cool 30 minutes.
Using the end of a wooden spoon, poke holes throughout the top of the cake.
Prepare instant pudding with cold milk in a mixing bowl, then pour slowly over top of cake.
Refrigerate for at least 2 hours.
Top with container of whipped topping, then sprinkle cereal over top, then serve and enjoy!