Preheat the oven to 350°F and line a cupcake pan with metallic or New Year’s themed liners.
In a large bowl, mix the cake mix, champagne, milk, oil, sour cream, eggs, and vanilla until smooth and well combined.
Divide the batter evenly between the cupcake liners and bake for 18 to 20 minutes, until the tops are set and lightly golden. Let them cool completely.
To make the frosting, beat the butter until creamy. Gradually add the powdered sugar, then mix in the champagne and vanilla until light, fluffy, and smooth.
Frost the cooled cupcakes and finish with edible stars, bows, or any sparkle-forward New Year’s decorations you love.