Mix all the ingredients in a large bowl and use a fork to blend everything. With your clean hands, press the mixture to make large clusters. Spread them on a lined baking sheet and bake for 20 minutes. Let it cool down before spreading over the cake.
½ cup Granulated sugar, ¼ cup Brown sugar, ½ teaspoon Baking powder, ¼ teaspoon Salt, ¼ cup Oil, 1 tablespoon Vanilla extract, ¼ cup Rainbow sprinkle, ¾ cup Flour
Assembly
Cut the cake into two separate sheets. Brush the cake surface with the milk soak.
Spread the frosting all over the bottom sheet. Place the second cake sheet on top of the frosting and brush it with milk soak. Frost the entire cake with the remaining frosting.
Generously sprinkle the top with cake crumbs. Let the cake sit for one hour before serving. This helps the cake absorb the soak.