Peel the mango. Using a sharp knife, remove the meat of the fruit from the pit. Cut the fruit into bite-sized pieces and place in a medium bowl. Sprinkle with sugar and let sit for 10 to 15 minutes.
Place the macerated mango in a food processor or blender. Puree until fruit is a smooth; add water 1 teaspoon at a time to thin out the puree if needed.
Pour your Moscato and the mango puree into a large pitcher. Stir to combine. Add the soda water. Store in refrigerator until ready to serve.
Give the spritzer a stir before pouring into a collins or hurricane glasses over ice.
Notes
You can add ice to the pitcher right before serving if desired. Just don't leave the pitcher sitting in the fridge with a bunch of ice in it for a long time, or it'll water down the cocktail.