In a saucepan over medium-heat, combine the sugar, corn syrup, butter and water.
Stir and heat to hard-crack stage or 300°F
Remove from heat and add the vinegar
Pour slowly over popcorn while stirring. Wait 5 minutes and shape into fist-sized round balls
Wrap each ball with plastic wrap to keep fresh
Notes
For true authenticity, skip the candy thermometer and get a bowl of ice water. As the sugar heats, you can pour a couple drops into the water to test the candy stages.
If you want to blow people's minds, find and toss as much as the unpopped kernels as possible. You won't get the thrill of danger of potentially cracking your teeth, but there's always sacrifices.