Easy Banana Pudding Cake

Step 1
Preheat oven to 350 degrees F (175 degrees C). Spray a 9×13-inch baking dish with cooking spray.

Step 2
Mix cake mix, water, eggs, and oil in a bowl until just moistened; pour cake batter into prepared baking dish.

Step 3
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 34 to 38 minutes. Cool in the baking dish for 2 to 3 minutes. Poke several holes into the cake using the handle of a wooden spoon. Be sure to poke all the way through to the bottom of the cake.

Step 4
Stir milk and pudding mix together in another bowl until smooth. Let pudding rest until it begins to thicken slightly, but is not fully set, about 2 minutes. Pour pudding over cake and spread evenly, making sure to fill each hole completely. Chill cake in the refrigerator until cake is cooled and pudding is set, about 2 hours.

Step 5
Spread whipped topping over cake and sprinkle with crushed vanilla wafers just before serving.