Rinse the berries and air-dry on paper towels. Place berries in a 6-cup jar; set aside. In large saucepan, combine vinegar and sugar; bring almost to a boil over low heat, stirring constantly, until sugar is dissolved. Do not boil. , Pour hot vinegar mixture over berries; cover jar tightly and let stand at room temperature 48 hours. Strain through several layers of cheesecloth into a sterilized bottle or jar. Seal tightly with a cork or lid. Store in cool dark place.