Cut a wedge of lime and run it around the rim of a margarita or low-ball glass.
Pour coarse salt onto a plate and dip the rim of the glass in the salt.
Fill a cocktail shaker half-full with ice. Add in the tequila, lime juice, and Swerve to the shaker.
Seal it and shake well until outside is frosted. It will take you about 10 to 15 seconds.
Add ice to the prepared glass, then strain margarita into it.
Top it off with sparkling water and stir.
Finally, garnish the glass with a lime wedge.