In a medium saucepan, combine water, butter, and salt. Bring to a boil over medium heat.
Remove from heat and add the flour all at once. Stir vigorously with a wooden spoon until a smooth ball of dough forms and pulls away from the sides of the pan.
Let the dough cool for about 5 minutes. Then, beat in the eggs one at a time until fully incorporated and the dough is smooth and glossy.
Transfer the dough to a piping bag fitted with a large star tip.
In a shallow dish, mix together the sugar and cinnamon for the coating.
Heat the oil in a deep skillet or Dutch oven over medium-high heat to about 350°F (175°C).
Carefully pipe about 4-6 inch strips of dough into the hot oil, cutting them off with kitchen scissors or a knife.
Fry the churros in batches for about 2-3 minutes per side, or until golden brown and crispy.
Remove the churros with a slotted spoon and drain on paper towels.
Immediately toss the warm churros in the cinnamon-sugar mixture until evenly coated.
Serve warm, optionally with chocolate sauce for dipping.
Notes
Churros are best enjoyed fresh. For dipping, a simple melted chocolate or dulce de leche sauce is a popular choice.