In a medium saucepan, combine water, sugar, salt, and butter. Bring to a boil.
Once boiling, remove from heat and stir in the flour until it forms a smooth dough.
Fill and heat a deep pan with about 2 inches of frying oil.
Spoon the dough into a piping bag fitted with a star tip.
Pipe 4–6 inch strips directly into the hot oil (use scissors or a knife to cut the dough).
Fry until golden brown, about 2–3 minutes per side.
Drain on paper towels.
While still warm, roll churros in the cinnamon-sugar mixture.
