Preheat oven to 350 degrees F and line a cupcake pan with cupcake liners and set aside.
Combine milk, egg whites, and extracts in a small bowl and whisk together and set aside.
In a large bowl or stand mixer fitted with a whisk attachment, add the flour, sugar, baking powder, and salt and mix on low speed for 30 seconds.
Cut the butter into small cubes and add to the dry ingredients. Mix on low speed until mixture resembles moist crumbs, about 3 to 4 minutes.
Add half of the milk and egg mixture to the dry ingredients and beat on medium speed for 90 seconds, scrape down the sides of the bowl and then add the remaining milk and egg mixture and beat until fully incorporated.
Add rainbow sprinkles to a small bowl with 1 teaspoon of flour and stir to coat, then add the sprinkles to the batter and mix for about 15 seconds until incorporated.
Add 1/4 cup of batter to each cupcake liner. Bake for 18-22 minutes depending on size until toothpick comes clean from center of cakes. Remove from oven and cool for a couple of minutes in the pan before transferring to a cooling rack.