Preheat oven to 350 degrees. Mix juice with the rest of the ingredients with a hand mixer until combined. On medium speed, mix for another 2 minutes.
Fill mini cupcake tins lined with wrappers 2/3 of the way full. Bake 10-12 minutes until a toothpick inserted in the middle comes out clean. Place on a wired rack for 5 minutes, and then transfer cupcakes directly on to a rack. Cool completely.
Champagne Buttercream Frosting
Cream together the butter and sugar with a hand mixer on medium speed. Add in the remaining ingredients and whip on high speed for two minutes until light and fluffy.
Top cupcakes with frosting and sprinkles, if desired. Serve and enjoy!