Mix the cake ingredients together until a smooth batter forms. Then gently fold in the colored sprinkles.
Evenly divide the batter between two round cake pans and bake at 350°F for 30 minutes.
Carefully level the top of the cakes for a smooth surface, and then cut them both in half.
Make the buttercream frosting, divide into three separate bowls, and dye each one a different color with food coloring. Spread the first color over the bottom cake layer.
Lay the second cake layer on top of the buttercream frosting and continue with the next color.
Once you have 4 cake layers and 3 buttercream frosting layers, make the outer layer frosting and spread it evenly over the entire cake, making sure to spread an especially thick layer over the top.
Sort your gummy bears by color and firmly press them into the frosting. Arrange them in a fun rainbow effect.
Add a bunch of gummy bears to the top of the cake for the crowning glory. Chill the cake before serving to help the gummy bears set.