Put the popcorn, sugar, oil and vanilla in a stovetop popcorn maker with a crank or a large saucepot with a lid. Turn the stove to medium heat. Close the top and crank (or place the lid on the pot and shake). Crank (or shake) until the popping stops, then remove from the stove top. Pour the kettle corn onto a baking sheet. Wait until the kettle corn cools. Break into pieces any corn that may have stuck together.