Grease and flour bottom of a 9x13-inch cake pan.
Preheat oven to 350 degrees F.
Add flour, baking soda, baking powder, and salt to a mixing bowl and whisk until combined, set aside.
In the bowl of a stand mixer or using a hand mixer, add butter, sugar, and vanilla extract, beat until creamy.
Beat in the milk then add in eggs one at a time, beating until just combined.
Add flour into butter mixture in batches and mix until combined.
Pour into prepared pan and bake for 32-35 minutes or until golden brown and a toothpick comes out clean, set aside to cool completely.
Prepare frosting while cake is cooling. To make frosting, add butter and vanilla to the bowl of a stand mixer or in a mixing bowl if using a hand mixer. Beat until creamy on medium-high speed, about 2 minutes.
Add powdered sugar to butter mixture in batches and beat until smooth, then beat in milk.
Fold in the sprinkles, then frost cooled cake.
Top with extra sprinkles if desired, cut, and serve.