Preheat oven to 350 degrees and line a muffin pan with cupcake liners. In a large bowl, mix together the butter, eggs, milk and yogurt. Add dry cake mix and blend until smooth.
Divide batter evenly into three smaller bowls. Dye one bowl of batter blue and one red, using the dye packets. Blend completely to incorporate color. Spoon each color of batter into a piping or plastic storage bag and secure the ends using a twist tie or rubber band. Lay the bags on a flat surface and tape them together so they are secured next to each other.
Hold the bags over one of the cupcake liners, then carefully cut off the ends at the same time. Fill each cupcake liner 3/4 full. Bake 17-20 minutes, until a toothpick inserted in the center comes out clean. Cool completely on a wire rack.
To make the frosting, blend the butter and yogurt together in a large bowl. Add dry frosting mix and blend a minute more until smooth and creamy. Divide frosting evenly into three bowls. Dye one bowl of frosting red and one blue, using the dye packets. Once the cakes have cooled, use a butter knife or spreader to frost each cupcake.
Frost a strip of white frosting into the middle of each cupcake, then dip the frosting into the white sparkling sugar. Repeat with the blue and red frosting and sparkling sugar, on either side of the white frosting section.
Garnish with small plastic or wooden spoons!