Preheat oven to 400° F degrees and grease your muffin pan with non-stick spray.
In a large mixing bowl add flour, baking powder, salt, sugar, and brown sugar and mix until combined.
In a separate bowl add milk, yogurt, egg, vanilla extract, and oil.
Begin adding the dry mixture to the wet mixture and stir until just combined. Make sure not over mix even if little flour mix are there, do not worry leave it.
Add 1/4 cup of rainbow sprinkles and gently fold into the batter until they’re evenly mixed in the batter.
Using a tablespoon cookie dough scoop, scoop the batter into muffin cups, filling them 2/3 of the way full.
Sprinkle additional rainbow sprinkles on top of each muffin.
Bake in the oven at 400 degrees for 8 minutes or until slightly browned on the sides.
Remove muffins from tins and let them cool on a baking rack for 5 minutes before serving.
Store leftover birthday cake muffins in an airtight container for up to 3 days.