Preheat oven to 350°F. Mix cake mix, milk, oil, egg whites and 2 teaspoons of the coffee extract in large bowl with electric mixer on low speed 1 minute. Beat on medium speed 2 minutes. Spoon batter into 24 paper-lined muffin cups, filling each cup 2/3 full.
Bake 18 to 20 minutes or until toothpick inserted into cupcake comes out clean. Cool in pans on wire rack 5 minutes. Remove from pans; cool completely.
Beat butter and remaining 2 teaspoons coffee extract in large bowl with electric mixer on medium speed until light and fluffy. Gradually add confectioners' sugar, beating until well blended after each addition. Add water; beat until light and fluffy.
Make an indentation in the center of each cupcake using the handle of a wooden spoon or a straw, making sure not to break through bottom of cupcake. Spoon 1/2 of the frosting into resealable plastic bag. Cut a small piece off one of the bottom corners of bag. Pipe frosting into each cupcake. Spread top of cupcakes with remaining frosting.