Combine sugar and corn syrup in a 1 1/2-quart microwave-safe bowl, stirring well.
Microwave at HIGH 4 minutes; stir in pecans. Microwave at HIGH 5 to 7 minutes or until lightly browned. Stir in butter and vanilla; microwave 1 minute. Stir in soda until foamy.
Pour mixture onto a lightly greased baking sheet; cool on pan on a wire rack. Break into pieces, and store in an airtight container.