Place frosting in a quart size baggie. Snip the corner and pipe on a pile of frosting in the center of the brownie.
Shake on the on confetti sprinkles.
Take the sour belts and cut into 1-2 inch strips.
Place a dollop of frosting towards the back center of the brownie. Then add a little frosting on the bottom edge of the candy strip. Place the strip in front of the frosting and push down a little. This will allow the rainbow to stand up and not fall over.