Rainbow Cake in a Jar

This is such a great idea I saw on Pinterest. So I made some for Mary's birthday.

Just make a boxed white cake according to the directions on the box.
Pour the batter into 4ish different bowls and color each a different color with food coloring:

Pour 1/3 of each color into 3 pint sized mason jars that are sprayed with oil:

Place jars into baking dish with about 1/2" of water in the bottom. 
Bake at 350 degrees for 30-35 minutes.

Top with frosting and sprinkles!