Preheat the oven to 350 and prepare a cookie sheet with parchment paper. Set to the side.
Using a hand or stand mixer with a paddle attachment, cream the butter with the sugars until light and fluffy, about 2-3 minutes. Add in the egg, followed by the vanilla, scraping down the sides of the bowl as needed.
Add in the cake mix, baking soda, and salt. Mix until combined.
Add in the sprinkles and mix them in with a rubber spatula.
Scoop the cookie dough using a cookie dough scoop. Place the cookie dough balls on the prepared cookie sheet and bake the cookies in the oven for 10-12 minutes until the edges are golden brown. If desired, you can roll the cookie dough balls in sprinkles before placing them in the oven.
Let the cookies cool slightly on the cookie sheet before transferring them to a cooling rack to fully cool.
