In a large bowl, blend cake mix, butter, egg, protein powder, and water together until smooth. The batter will be THICK and almost dough-like, but you can add more water if necessary.
Add in white chips and some of your sprinkles.
Spray a small brownie pan with nonstick (8x11 or smaller), and spread batter out into an even layer. Smooth down with a spatula or your hands.
Generously add sprinkles on top and press down slightly into batter.
Bake at 35o degrees for 20-25 minutes or until golden brown.
Cut into 2-3 -inch pieces and serve.