Combine butter, sugar, salt, and water in a medium saucepan.

Bring to a boil over medium heat.

Add flour all at once.

Stir vigorously until the mixture leaves the sides of the pan and forms a smooth ball.

Remove from heat.

Stir in vanilla extract.

Add eggs one at a time, beating with a wooden spoon after each addition until smooth.

Pour oil to a depth of 2 inches in a large Dutch oven or heavy saucepan.

Heat oil to 370°F (185°C).

Spoon batter into a large decorating bag fitted with a large star tip.

Pipe batter in 6-inch strips into the hot oil, in batches.

Fry for 3 minutes or until golden, turning once.

Lift out with a wire spatula and drain on paper towels.

Combine sugar and cinnamon in a shallow dish.

Roll churros in sugar mixture.

Repeat with remaining batter.

Serve immediately.