For the CupcakesPreheat oven to 325 degrees. Line mini muffin tins with cupcake liners. In large bowl, beat cake mix, water, oil and eggs with electric mixer on low speed about 30 seconds, increase speed to medium and mix until smooth, about 2 minutes. Pour into prepared pans and bake until a toothpick inserted into center of cupcake comes out clean, 15 to 18 minutes. Cool in pans for 5 minutes then cool completely on wire rack.
For the Mango ButtercreamPuree one and a half diced mango in food processor or blender until smooth, set aside (will yield about ¾ cup). Reserve remaining diced mango for garnish.
In a large bowl, beat butter with electric mixer on medium speed, until smooth; slowly add powdered sugar, 1 cup at a time, mixing between each addition.
Add ¾ cup mango puree. Increase speed to high and beat until incorporated, about 2 minutes.
Transfer buttercream to a piping bag fitted with a pastry tip or a large zip top bag and top cooled cupcakes with buttercream. Top with 1 piece diced mango and sparkling sugar if desired.
Each serving (1 mini cupcake) contains 163 calories, 22 g carbohydrate (7% Daily Value), 0.1 g fiber (1% Daily Value), 1 g protein (2% Daily Value), 8 g fat (13% daily value), 4 g saturated fat (18% Daily Value), 24 mg cholesterol (8% Daily Value), 78 mg sodium (3% Daily Value), and 27 mg potassium (1% Daily Value).