Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan with nonstick spray.
In a large bowl, mix together 1 box of strawberry cake mix, 1 cup of milk, 1 stick of melted butter, 4 eggs, and 1 teaspoon of vanilla extract until the mixture is smooth.
Pour the batter into the prepared pan and bake for 25 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool for 10 minutes, then use a chopstick to poke holes all over the cake.
In another large bowl, whisk together the remaining 4 cups of milk, 1 teaspoons of vanilla extract, and 2 packages of banana pudding mix until the mixture thickens, about 1-2 minutes.
Pour the pudding over the cake, spreading it evenly. Cover the cake and refrigerate for 1 hour, or until the pudding sets.
Spoon frosting over the chilled cake and swirl it into a light pink, creamy topping, about 2 minutes.
Before serving, decorate the cake with sliced bananas and strawberries. Add the bananas just before serving to prevent them from browning.
Store any leftover cake covered in the fridge for up to 3 days.