Preheat the oven to 350°F. Generously grease and flour a 10-cup Bundt pan and set it aside.

In a large bowl, beat the cake mix, cheesecake instant pudding mix, sour cream, milk, vegetable oil, eggs, and vanilla extract with a hand mixer until well combined. Mix on low speed for 30 seconds; scrape the edges of the bowl. Beat on medium speed for 1-2 more minutes, until well combined.

In 3 separate bowls, add 1/2 cup of batter into each one. Add a few drops of food coloring (one color per bowl) to the batter, stirring well after each addition until the batter reaches your desired color.

In the bundt pan, pour all of the white batter and spread evenly. Place spoonfuls of each colored batter randomly into the prepared pan. Gently run a butter knife back and forth through the batter a few times to swirl the colors (don’t swirl too much, or it will all blend together and turn brown).

Bake for 30-35 minutes or until a toothpick inserted into the middle comes out with only a few crumbs.

Remove from the oven and cool completely before applying the glaze.

To make the glaze, add the powdered sugar and melted butter to a medium bowl; stir until combined.

Whisk in the milk and vanilla, mixing until completely smooth. If you’d like the glaze to be thinner, add more milk 1 tablespoon at a time until it is a pourable consistency.

Pour the glaze over the cooled cake, letting the glaze drip down the sides.

Immediately top the glaze with sprinkles.

Allow the glaze to set before slicing and serving.