Combine 1 1/2 tablespoons granulated sugar and kosher salt in a dish. Cut lime into 9 wedges; rub rims of 8 glasses with 1 lime wedge.

Dip rims of glasses in salt mixture. Combine water and 1/2 cup sugar in a microwave-safe glass measuring cup. Microwave at HIGH 2 1/2 minutes, stirring to dissolve sugar; cool.

Combine syrup, tequila, Grand Marnier, fresh lime juice, and blackberries in a blender; process until smooth. Strain mixture through a cheesecloth-lined sieve over a pitcher; discard solids.

Serve over ice. Garnish with remaining lime wedges.