Muddle the honey and sage together in a cocktail shaker. Add the vodka in and use the muddler to stir, dissolving the honey into the vodka. Add ice to the shaker, pour the grapefruit juice over the ice. Fix the lid in place and shake vigorously.
Fill 2 cocktail glasses with ice. Strain the contents of the cocktail strainer into the glasses. Garnish each glass with 2 quarters of grapefruit and a fresh sage leaf.