Rub the rim of a margarita glass with a lime wedge. Dip the rim into the coarse salt.. Fill the glass halfway with ice. Set aside.
Fill a cocktail shaker with ice and the tequila, triple sec, lime juice, and prickly pear syrup. Shake for 30 seconds then strain into prepared glass.
Top with sparkling water.
Garnish with a lime wedge and a slice of prickly pear.