Combine rhubarb, sugar, and vinegar in a medium pot. Heat over medium, stirring constantly, until sugar is dissolved.
Continue cooking until rhubarb starts to breakdown and fall apart, stirring frequently.
Remove mixture from heat. Allow to cool for 5 to 10 minutes.
Place fine mesh strainer over a medium bowl, then add rhubarb mixture. Stir the mixture as it drains and press gently on the pulp, to remove as much liquid as possible.
Transfer shrub to a mason jar (or other airtight container), then refrigerate until cold.
Make cocktail:
Mix together 1 to 1 ½ ounces of the shrub (to taste) and 1 ½ ounces gin in a rocks glass.
Fill glass with ice, then top off with sparkling water.
Stir drink, then serve immediately. Enjoy!
Notes
The shrub recipe makes about 1 ½ cups of syrup, enough for multiple drinks. Save the leftover rhubarb pulp after straining out the syrup. It can be used as a sweet, tangy jam on toast, bagels, and more.Make sure to read the info before the recipe card for helpful tips, recipes variations, and more!