Combine sugar, syrup, and vinegar into 2 quart mixing bowl. Cover and microwave at high 3 minutes; stir well. Microwave, uncovered, at high 4 1/2 to 10 minutes until thickened (300 degrees). Test by dropping small amount in cold water. Remove threads from water. If threads bend microwave a little longer. Candy is done if threads break. Quickly stir in soda; mix well to prevent baking soda lumps. Mixture will foam up as soda is added. Pour into buttered, foil-lined 8 x 8 inch or 9 x 9 inch baking dish, allowing mixture to spread itself. Let stand until firm. Remove from dish and break into pieces. If desired, you can dip them into melted chocolate (chocolate chips work well).