Pour coconut sugar on a plate and set aside.
Rim the edge of a lowball glass with a grapefruit wedge, careful not to get its pulp on the glass.
Dip the rimmed glass into the plate of coconut sugar until the rim is completely coated with sugar.
Pour the fresh grapefruit juice, lemon juice, and maple syrup into the rimmed glass and stir until well combined.
Add a shot of vodka to the grapefruit mixture.
Add ice and top with club soda until the glass is full.
Serve with a slice of grapefruit and a sprig of fresh rosemary.
