On a plate, combine unsweetened shredded coconut, lime zest, and kosher salt. Run a lime wedge around the rim of the glasses and dip them in coconut salt mixture to coat.
To a cocktail shaker, add guava nectar, tequila, coconut water, lime juice, agave, and a few ice cubes. Cover and shake vigorously for 10 minutes. Taste and adjust for sweetness.
Add ice cubes to the prepared glass. Pour the guava margarita into the glass and garnish it with a lime wedge. Enjoy!