Preheat oven to 250°F (120°C). Line baking sheets with parchment paper.
Combine butter, corn syrup, and cinnamon candies in a pot over medium heat. Bring to a boil, and cook for 5 minutes. Pour the syrup over the popcorn in a large, heatproof bowl, and stir to cover the popcorn as evenly as possible. Spread the popcorn out onto the prepared baking sheets.
Bake in the preheated oven until the candy coating is set, about 30 minutes.