Shrub, the sweet-tart syrup favoured by colonial Americans, is simply made by macerating fruit in sugar until the fruit exudes its juice, straining, then adding vinegar. Mixed with rum and soda, it makes a bracing drink, ideal for summer afternoons.
2 oz dark rum
½ oz shrub syrup
Combine rum and syrup in an ice-filled Collins glass.
Top with club soda and stir gently to combine.