In a large saucepan, combine sugar, corn syrup and water; bring to a boil,
stirring constantly, until sugar is dissolved. Cook, without stirring, over
medium heat until a candy thermometer reads 300 degrees F (hard-crack stage).
Remove from the heat; stir in butter, vanilla extract and baking soda.
Pour into a greased 15 x 10 x 1-inch jellyroll baking pan.