In a glass with ice, pour in Campari and Prosecco.
Top with sparkling water. Stir to combine.
Garnish with a slice of orange.
Notes
If you want to sweeten the bitter taste, you can add half an ounce of simple syrup to your drink.
This is a low ABV (alcohol by volume) drink; however, you can make it even lower by replacing the Prosecco with more sparkling water or a n/a sparkling wine.
Garnish ideas - Herbs, citrus fruits, rhubarb or a cherry.