In a medium saucepan, combine the water, granulated sugar, salt, and vegetable oil. Bring to a boil over medium heat.
Remove from heat and immediately stir in the all-purpose flour. Stir vigorously until the mixture forms a ball.
Let the dough cool slightly, then beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract until the dough is smooth and glossy.
Heat about 2 inches of vegetable oil in a large, heavy-bottomed pot over medium-high heat until it reaches 375°F (190°C).
While the oil is heating, transfer the dough to a piping bag fitted with a large star tip.
Carefully pipe 4-6 inch lengths of dough into the hot oil, using scissors to cut the dough as you pipe. Fry the churros in batches, turning occasionally, until golden brown and crispy, about 2-3 minutes per side.
Remove the churros from the oil with a slotted spoon and drain on paper towels.
In a shallow dish, mix the granulated sugar and ground cinnamon.
While the churros are still warm, roll them in the cinnamon sugar mixture to coat evenly.
In a small saucepan, combine the dulce de leche and heavy cream. Heat over low heat, stirring constantly, until the sauce is warm and smooth.
Serve the churros warm with the dulce de leche sauce on the side for dipping.
Enjoy your meal!