Place blueberries in a sterilized 1-quart glass jar. Combine vinegar and sugar in a nonaluminum saucepan over high heat. Cover and bring to a boil. Remove from heat, and pour vinegar mixture over blueberries. Cover and let stand at room temperature 3 days.
Strain blueberry mixture through several layers of damp cheesecloth into decorative jars; discard blueberries. Seal jars with a cork or other airtight lid. Yield: 2 cups (about 7 calories per tablespoon).