Preheat the oven to 350 degrees. Line cupcake pan with paper cupcake liners.
Add cake mix and soda to a large bowl or bowl of a stand mixer, and beat on medium for 2 minutes.
Fill cupcake liners halfway with cake batter.
Bake for 15-20 minutes, until you can insert a toothpick, and it comes out clean. Cool for 1 hour on a baking rack.
Fill a ziplock bag or piping bag with frosting. Pipe frosting onto cupcakes by starting in the middle, swirling around the cupcake, then meeting back in the middle.
Top each cupcake with a root beer barrel candy. Cut straws in half, then in half again (each straw will give you 4 mini straws), and insert a mini straw into each cupcake.
Notes
Add a splash of root beer extract to the frosting. If you want stronger soda flavor, a small amount of root beer extract in the buttercream makes the flavor pop without overpowering the chocolate.
Use Regular Root Beer: Better flavor and structure.
Don’t Overmix: Keeps cupcakes light.
Cherry: Add whipped cream and a cherry on top to make it look like a root beer float.