Heat sugar, corn syrup and vinegar to boiling in a 2-quart saucepan over medium
heat, stirring constantly, until sugar is dissolved. Boil without stirring, to 300
degrees F on candy thermometer (hard ball stage).
Remove from heat. Quickly stir in baking soda thoroughly.
Pour mixture into ungreased 13 x 9-inch pan. Do not spread!
Cool, then break into pieces.
Candy can now be dipped
into chocolate coating if desired.