For the crumb cake: Preheat oven to 350 degrees and spray the baking dish with non-stick spray.
Using a large bowl, whisk the flour, baking powder, baking soda, salt and the rainbow sprinkles until combined.
Using a standing mixer, beat together the sugar, butter, brown sugar, eggs, vanilla and sour cream until combined and fluffy.
Alternate between the dry ingredients and the milk and beat until combined. Pour the batter into the baking dish and set aside while you make the crumb topping.
For the crumb topping: Using a medium to large bowl, combine the flour, sugar, brown sugar, salt and sprinkles until combined.
Using your fingers or spoon, cut the butter into the dry ingredients to create a crumb mixture.
Sprinkle the crumb topping onto the batter and sprinkle some more rainbow sprinkles on top.
Bake in the preheated oven for 45-60 minutes or until a toothpick inserted into the center of the cake comes out clean.
If you choose to use the sugar glaze you will mix that together until it is smooth and drizzle it across the cake before serving.
