Launch into the days of summer with a refreshing drink to hydrate, refresh, and cool off. This is one of my favorite summer beverages and it makes use of the season’s sweet strawberries. It’s called a shrub, or a tonic, which is a syrup composed of fruit, sugar, and vinegar. Also known as drinking vinegar, shrubs are an old-fashioned method of preserving fruit by mixing soft, ripe produce with vinegar and sugar, then letting the mixture sit for a few days to mingle and macerate before straining out the solids. Nowadays, shrubs are enjoying a resurgence, back in vogue as a cleansing refreshment, as well as a flavorful syrup for cocktails. The combinations are numerous and open to creative inspiration, bearing in mind a few rules of thumb: Use ripe, untreated, soft fruit such as berries and stone fruit at the peak of season, and wash thoroughly. Blend with a …