1Heat oven to 350°F. Spray 24 mini muffin cups with cooking spray.
2In large bowl, beat cake mix, water, oil and egg whites with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes. Fill muffin cups half full with batter. (Cover and refrigerate remaining batter until ready to bake; cool pan before reusing and spray again with cooking spray.)
3Bake 10 to 15 minutes or until toothpick inserted in center comes out clean. Remove cupcakes from pans to cooling racks; cool completely, about 15 minutes. (Repeat with remaining batter to make about 48 additional mini cupcakes. Freeze cupcakes for another use.)
4Spoon frosting into decorating bag (fitted with desired tip) or resealable food-storage plastic bag (with small corner cut off). To assemble, drop 1 cupcake into each push-up pop container; pipe desired amount of frosting on cupcake. Top each with second cupcake; pipe with frosting. Garnish with strawberry and mint sprig.