Combine sugar, water, vinegar, and butter in a 2-quart saucepan; cook over medium heat, stirring constantly, until sugar dissolves. Cover and continue to cook over medium heat 2 to 3 minutes to wash down sugar crystals from sides of pan. Uncover and cook, without stirring, until mixture reaches soft crack stage (270°). Remove from heat, and stir in vanilla.
Pour syrup into a well-buttered 15- x 10- x 1-inch jellyroll pan or onto a well-buttered marble slab. Allow syrup to cool slightly.
Work syrup into a mound, using a buttered spatula or candy scraper. Divide mound of candy in half. With buttered hands, pull, fold, and twist each portion until candy is opaque and begins to stiffen.
Pull each portion into a rope, 1/2-inch in diameter. Twist ropes together, forming 1 rope. Cut into 1-inch pieces; wrap each piece in waxed paper.