In a stand mixer fitted with the paddle attachment, mix together 5 pounds cake mix, 30oz water, and 5oz oil on low until it comes together. Mix on 2nd speed for 2 minutes. Stir in 20oz sprinkles by hand. Using a #40 or plum disher, scoop .5oz. scoops onto sheet tray lined with parchment paper. Bake at 375*F for 10-12 minutes. Once cooled, using a straight tip, pipe a swirl of buttercream in the center of half the cake circles, top each with another half.