Mixing it Up
Shrubs originated as a food preservation technique that dates back to the days before refrigeration. To prolong the life of ripe fruits, adding them to a crock with a good amount of sugar would transform them within a few weeks to vinegar. This vinegar, though, has the bright, fragrant fruit flavors and could be best described as a vinegar “syrup.”
Serious Eats better puts it, “a proper shrub has a flavor that’s both tart and sweet, so it stimulates the appetite while quenching thirst.”
"Colonial-day shrubs were spiked with liquor (usually brandy or rum) but today these fruit juice, sugar and vinegar drinks are usually non-alcoholic. Shrubs are served over ice, with or without soda water."
The New Food Lover’s Companion, page 699