Preheat oven to 350° F Grease a 13x9-inch baking pan with cooking spray.
Combine cake mix, eggs, milk, vanilla, and cinnamon in a large mixing bowl.
Beat with a hand mixer to combine until well incorporated. Pour into prepared pan.
Bake 30-35 minutes or until a toothpick inserted in center comes out clean. Cool in pan on a wire rack 20 minutes.
Use a chopstick or skewer, and generously poke holes in top of the warm cake. Pour milk mixture slowly over cake, and let the mixture absorb and fill the holes.
Just before serving, add cream, confectioner’s sugar and vanilla, and beat until it begins to thicken. Continue to beat until soft peaks form. Spread over cake.
(Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.)