• Preheat oven to 350°F.
• In the bowl of a stand mixer fitted with the paddle attachment or in a large mixing bowl with an electric hand mixer, beat together the cake mix, pudding mix, sour cream, oil, eggs, vanilla, and water. Beat for about 2 minutes on medium speed until well combined.
  1 (15.25-ounce) box yellow cake mix, 1 (3.4-ounce) box instant vanilla pudding mix, ¾ cup sour cream, ¾ cup vegetable oil, 3 large eggs, 2 teaspoons pure vanilla extract, ½ cup warm water

For a 9-inch layer cake:

• Grease (2) 9-inch cake pans. Divide batter evenly between the two pans, spreading to the edges with a spatula.
• Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center of the cakes comes out clean. Allow to cool for 15 minutes in the pans before turning the cakes out onto a wire rack to cool completely.
• Fill and frost cooled cakes with your favorite frosting, such as chocolate buttercream.

For a 9x13-inch sheet cake:

• Grease (1) 9x13-inch cake pan and/or line with parchment paper. Pour batter into the pan and spread to the edges with a spatula.
• Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted in the center of the cake comes out clean.
• Let cake cool completely on a wire rack before topping with your favorite frosting.