Divide marshmallows into 24 groups of 14 marshmallows each (336 total).
Starting with one bunch of marshmallows, use kitchen shears or scissors to cut each in half diagonally. Dip cut sides of 14 of the marshmallow halves in a light-colored sparkling sugar. Dip remaining 14 halves in the darker companion color of sparkling sugar.
Spread top of one cupcake with frosting. Press flat side of each marshmallow half into frosting, alternating light and dark colors in concentric circles on cupcake.
Repeat with remaining cupcakes. Arrange cupcakes on a platter to resemble a bunch of cut flowers. Place green-apple-flavored candy sticks or candy string, tied with a ribbon, to resemble flower stems.
If desired, add green "leaves" to each cupcake: Snip 2 marshmallows in half diagonally. Dip cut sides in green sparkling sugar. Randomly attach to cupcakes, tucking under outer petals.