Preheat the oven to 350°F.

Generously grease with nonstick cooking spray or cake release.

Lightly flour a 10-cup Bundt pan.

To make the cake: In a large bowl with a hand mixer or in the bowl of a stand mixer, beat the cake mix, cheesecake instant pudding mix, sour cream, milk, vegetable oil, eggs, and vanilla extract.

Mix on low speed for 30 seconds; scrape edges of the bowl.

Beat on medium speed for 1-2 more minutes, until well combined.

In 3 separate bowls, add ½ cup of batter into each one.

Add a few drops of food coloring (one color per bowl) to the batter, stirring well after each drop, until the batter reaches your desired color.

In the bundt pan, pour all of the uncolored cake batter and spread evenly.

Place spoonfuls of each colored batter randomly into the prepared pan with a cookie scoop. 

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 center of the cake comes out with only a few crumbs.

Let the cake cool completely (at least 1 hour) 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 glaze over the top off the cake, letting the glaze drip down the sides. 

Top this delicious treat with sprinkles, slice, and serve.