1 oz vodka (or gin)
1/2 oz lemon juice
Club soda or sparkling water
Grapefruit peel for garnish
Fill a tall glass with ice and add vodka and grapefruit shrub syrup. Stir well. Top off the glass with club soda or sparkling water and a pinch of sea salt if desired. Garnish with grapefruit peel.
For a healthy craft soda, just forego the vodka or gin.