Mix flour, sugar, and salt in a bowl.
Bring water and butter to a boil in a pot.
Add the flour mixture to the boiling water and knead the dough.
Let the dough cool, then put it into a piping bag.
Pour enough oil into a pan and preheat to 170°C.
Pipe the dough into churro shapes and fry them.
Remove the churros when they are golden brown.
Sprinkle with sugar and cinnamon to finish.