How to Make It
Preheat oven to 350°F. Combine cake mix, oil, eggs, egg whites, lime zest, lemon zest, and 1 cup of the Mountain Dew in the bowl of a heavy-duty electric stand mixer fitted with the paddle attachment. Beat on medium speed 2 minutes. Beat in green and yellow food coloring until desired shade of green is achieved. Pour batter evenly into 2 (12-cup) muffin pans lined with paper baking cups. Bake until done and lightly golden, 15 to 18 minutes. Cool completely, about 20 minutes.
Meanwhile, bring remaining 1 cup Mountain Dew to a boil in a small saucepan over medium-high. Cook at a rapid simmer until reduced to about 1 tablespoon, about 15 minutes. Cool completely, about 20 minutes. Stir Mountain Dew reduction into vanilla frosting. Add green and yellow food coloring until desired shade of green is achieved.
Spread cupcakes with frosting, and sprinkle with sparkling sugar sprinkles. Place 1 straw piece in each cupcake.