Place the peaches, sugar, and lime juice in a blender and blend until smooth.
Transfer the peach puree to a large cocktail shaker or large mason jar and add in tequila, peach liqueur, and triple sec. Add in some ice and shake vigorously for about 15 seconds.
Rub a lime wedge along the rims of 4 rocks glasses and and invert each glass into a small dish of coarse sugar.
Add ice cubes to each glass.
Divide the mixture between the 4 glasses and top off each cocktail with Mountain Valley White Peach Sparkling Water.