Combine the raspberries, vinegar, and sugar in a small jar, mashing the berries lightly with a fork until they release their juice.

Cover and refrigerate for at least 24 hours, shaking the jar once a day, until the sugar fully dissolves and the liquid turns deep pink; the shrub keeps refrigerated for one month.

Strain the shrub through a fine-mesh strainer into a clean jar, pressing on the solids to get every drop, and discard the pulp.

Fill a highball glass with ice.

Pour 1.5 ounces of the raspberry shrub over the ice.

Top with the chilled soda water and stir once, gently, to keep the bubbles.

Garnish with a few whole raspberries dropped in and a lemon twist on the rim.