Line a cookie sheet with aluminum foil.
In a large heavy saucepan over medium heat, combine corn syrup, sugar, and water. Stir mixture only until sugar is completely moist and mixture reaches 242 degrees F on a candy thermometer. At that point, without stirring, immediately remove from heat and add cinnamon. Stir until mixture settles or stops boiling. Stir pecans into mixture all at once. Stir until all pecans are coated completely. Pour out onto a cookie sheet and allow to cool. Break into pieces and serve.