Combine sugar, butter, and corn syrup in a small saucepan; cook over medium heat until thickened, stirring constantly.
Pour syrup mixture into a 13x9x2 inch baking dish.
Place 6 slices of bread on top of syrup mixture. Top with remaining 6 slices of bread.
Combine eggs, milk, vanilla, and salt, stirring until blended. Pour egg mixture evenly over bread slices.
Cover and chill 8 hours. Bake, uncovered, at350 degrees F. for 40 to 45 minutes or until lightly browned.