In a medium saucepan, combine water, butter, and salt. Bring to a boil over medium heat.
Remove from heat and add flour all at once. Stir vigorously until a dough forms and pulls away from the sides of the pan.
Transfer the dough to a mixing bowl. Let it cool for 5 minutes.
Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Transfer the dough to a piping bag fitted with a large star tip.
Heat about 2 inches of vegetable oil in a deep skillet or Dutch oven to 375°F (190°C).
Carefully pipe strips of dough into the hot oil, cutting them off with scissors. Fry for 2-3 minutes per side, until golden brown and cooked through.
Remove churros with a slotted spoon and drain on paper towels.
In a shallow dish, combine sugar and cinnamon. Toss the warm churros in the cinnamon sugar mixture until evenly coated.
Serve immediately.
