Place the strawberries in a large bowl, and use a potato masher or the back of a wooden spoon to mash the berries. Mash until juices begin to be released. Fold in the sugar, and stir until mostly dissolved. Cover and refrigerate overnight.

Set a fine-mesh strainer over a clean, wide-mouth jar, and strain the strawberry mixture through the sieve. Press lightly on the fruit to ensure all the juice is extracted. If any sugar is left at the bottom of the bowl, scoop it into the syrup. Add the vinegar, and whisk to combine. Cover and give the shrub a gentle shake. Refrigerate.

Enjoy after giving it at least a day or two to develop (see note). The flavors will change as the fruit acids and sugars dissolve. After one week, the granulated sugar should be completely dissolved. The shrub will keep, refrigerated, for up to 1 year.