1 box marble cake mix
1 1/2 Tbs. root beer extract
1 c. water
1/3 c. oil
Preheat the oven to 350 degrees. Line your cupcake tins with paper or foil liners. In a large bowl, whisk the above ingredients by hand. Pour evenly into 24 cupcake liners. Bake for 18-20 minutes until the tops are firm. Let cool fully before frosting.
For the frosting, I combined one container of vanilla frosting with about 1 1/2 tsp. root beer extract. Then I piped the frosting on top of the cupcakes with a star tip.