Preheat the oven to 250°F (121°C). Line 2 rimmed baking sheets with parchment paper and butter the parchment.
Discard any unpopped kernels from the popcorn. Divide the popcorn and crumbled bacon evenly between the baking sheets.
Place the sugar, butter, and corn syrup in a 2-quart or other deep-sided saucepan. Bring to a boil over medium heat, stirring constantly. Remove the pan from the heat and carefully stir in the bourbon, vanilla, salt, and baking soda. Be aware that the baking soda is going to make the mixture boil and bubble like you're in trouble, but you're not. It'll simmer down quickly.
Immediately pour the bourbon syrup evenly over the popcorn and bacon and, working quickly, toss everything with a lightly buttered spatula to coat it. (If you prefer, transfer the mixture to a large pot and toss it in there.) Spread the popcorn mixture in an even layer and bake for 50 to 60 minutes, stirring every 15 minutes. You want the candied popcorn to be sorta dry to the touch and, you know, done.
Spread the popcorn on a fresh sheet of parchment paper to cool, breaking apart large clumps once the popcorn is not too hot to handle. The popcorn will become crisper and crunchier as it drops in temperature. Store any leftover popcorn in an airtight container.