Preheat your oven to 350°F (175°C).
In a mixing bowl, cream together the softened butter, sugar, and brown sugar until fluffy.
Add the egg and vanilla extract, mixing until well incorporated.
In a separate bowl, whisk together the flour, cake mix, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until combined.
Fold in the sprinkles gently.
Scoop tablespoon-sized balls of dough onto a lined baking sheet.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for a few minutes before transferring to a wire rack.