To prepare your glass, run a slice of grapefruit around the rim of the glass. Pour coarse salt on a plate and press the rim of the glass into the salt.
To a cocktail shaker, add Tequila Blanco, fresh grapefruit juice, soda water, sugar syrup, fresh lime juice and ice. Shake till cold. Strain into prepared glass filled with ice. Add a slice of grapefruit to garnish.