Preheat the oven to 350 degrees and add the cupcake liners.
Add the cake mix to a bowl and mix in the eggs, oil, and soda on medium speed.
Pour the batter into the cupcake liners 2/3 of the way full. Put in the oven and bake for 18-20 minutes.
Frosting:
Mix the butter and beat it until it's fluffy - which will take about 2 minutes.
Mix the half and half (or milk) and root beer together in a different bowl. (This is important!)
Mix in the powdered sugar slowly, one cup at a time. Add a bit of the liquid mixture from above in between each cup of sugar. Mix for 1 minute or until the texture is creamy.
Add to a piping bag and frost the cooled cupcakes. Put a cherry and staw on top.