In a small mixing bowl, combine the granulated sugar and ground cinnamon. Stir until evenly blended and set aside for later use.

Pour vegetable oil into a deep fryer or heavy-bottomed pot, ensuring there is enough oil to submerge the duros completely. Heat the oil to 350°F (175°C). Use a thermometer to maintain an accurate temperature.

Carefully add approximately 15 duros to the hot oil at a time. For the first few seconds, no changes will be visible. However, they will quickly puff up into airy spirals. Allow the duros to cook for an additional 5 seconds after puffing to ensure they are fully cooked.

Using a slotted spoon, remove the fried duros from the oil and transfer them to a wire rack or a plate lined with paper towels to drain excess oil.

While the duros are still warm, generously sprinkle them with the prepared cinnamon sugar mixture. Toss gently to ensure even coating.

Transfer the coated cinnamon twists to a serving dish and enjoy them fresh and crispy. They pair wonderfully with coffee, hot chocolate, or as a standalone treat.