Preheat oven to 300 degrees F and line two baking sheets with parchment paper.
Into an extra-large mixing bowl, add the popped popcorn.
Into a small saucepan over medium heat, add brown sugar, vegan butter, light corn syrup, vanilla, and sea salt. Bring to a boil, stirring frequently.
Remove from heat and stir in baking soda.
Working quickly, pour the caramel over the popcorn. Stir to coat.
Divide the coated popcorn between the two parchment-lined baking sheets. Spread across the surface of each baking sheet so that popcorn is in an even layer.
Bake popcorn for 12 minutes.
Allow to cool completely before serving. Store in an airtight container.