Preheat the oven to 350°F (177°C). Generously grease and flour a 10–12 cup Bundt pan, making sure to get into all the crevices. Set aside.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large mixing bowl with a hand mixer, beat the butter and sugar together on medium speed until light and fluffy, about 2–3 minutes.
Add the egg whites and vanilla extract Mix until fully incorporated, scraping down the sides of the bowl as needed.
Alternate adding the dry ingredients and the milk. Mix just until combined. The batter will be thick.
Gently fold in the sprinkles with a spatula, being careful not to overmix.
Pour the batter evenly into the prepared Bundt pan and smooth the top.
Bake for 45–55 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Let the cake cool in the pan for 15 minutes, then carefully invert onto a wire rack and allow to cool completely before frosting.