Preheat oven to 350° F and line baking sheet with parchment paper or spray with nonstick cooking spray.
In the bowl of a stand mixer, or using electric beaters, cream together butter and sugars. Add egg and vanilla and beat together, scraping down sides of bowl as necessary.
Add flour, cake mix, baking soda, and salt and mix to combine. Stir in sprinkles.
Scoop dough out by rounded tablespoonful onto prepared baking sheet. Bake at 350° F for 10-12 minutes until edges are slightly browned.
Remove from oven and let cool for about 5 minutes before transferring to cooling rack to cool completely.