A shrub, aka a drinking vinegar at the most basic, is a mixture of equal parts sugar and vinegar with fruits or vegetables added. Here is a basic recipe, but you can experiment with different vinegars and sugars, even adding spices or fresh herbs or mixing fruit and veggie combinations.
In this picture, the tomato is on the left (with leftovers made into tomato jam) and a batch of watermelon and watermelon jam. Shrubs naturally separate in the refrigerator, so shake or stir before using.
1 pound tomatoes, cored and chopped
1/2 cup white balsamic vinegar
1/2 cup granulated sugar
In a medium saucepan combine all ingredients. Cook over medium heat, stirring occasionally, until the sugar dissolves and the tomatoes are very soft. Remove from heat, allow to cool. Place in a jar and store in the refrigerator overnight. Strain tomatoes from the liquid, keeping both. The liquid is the shrub and the tomato pulp can be used to make tomato jam, or just eaten as is.
Add the shrub to sparkling water, flat water, or your favorite spirit. I like to drink it over ice, on its own, without being diluted.
Mocktail
4 ounces shrub
2 ounces sparkling water
Combine and pour over ice