In a medium saucepan, combine the water, sugar, salt, and vegetable oil. Bring the mixture to a boil over medium heat, stirring occasionally until the sugar has dissolved.
Remove the saucepan from the heat and add the flour all at once. Stir vigorously with a wooden spoon until the mixture forms a smooth dough that pulls away from the sides of the pan.
Transfer the dough to a piping bag fitted with a large star-shaped nozzle. Alternatively, you can use a ziplock bag and cut off one corner to create a makeshift piping bag.
Heat vegetable oil in a deep fryer or a large pot until it reaches 375°F (190°C). Carefully pipe 4-6 inch long strips of dough directly into the hot oil, using scissors or a knife to cut the dough.
Fry the churros for about 3-4 minutes, turning occasionally, until they are golden brown and crispy. Use a slotted spoon to transfer the churros to a plate lined with paper towels to absorb any excess oil.
Repeat the frying process with the remaining dough, ensuring not to overcrowd the pan. Allow the churros to cool slightly before serving.