Prepare 2 quarts of popcorn using your preferred method and set aside in a large bowl.

In a saucepan, combine the corn syrup, brown sugar, water, and vinegar.

Cook the mixture over medium heat, stirring constantly, until it reaches the hard-ball stage (about 250°F/121°C on a candy thermometer).

Once the mixture reaches the desired temperature, remove it from the heat and stir in the margarine or butter until melted and well combined.

Pour the hot syrup mixture over the popcorn in the bowl.

Using a spatula or wooden spoon, quickly and carefully mix the popcorn and syrup until the popcorn is evenly coated.

Allow the mixture to cool slightly until it is cool enough to handle but still pliable.

With lightly greased or damp hands, shape the coated popcorn into balls, pressing firmly to ensure they hold together.

Place the formed popcorn balls on a baking sheet or wax paper to cool completely and set.

Once cooled and set, store the Sweet Popcorn Balls in an airtight container at room temperature.