In your heavy-bottomed pot, pour in 3 to 4 cups of vegetable oil. Heat the oil over medium heat until it reaches 350°F (175°C). Use a thermometer to ensure the oil is at the right temperature for frying.
Open the can of cinnamon rolls and separate each roll. Using your fingers, gently stretch each roll into a donut shape, making a hole in the center. Try to keep the thickness even for uniform cooking.
Once the oil is hot, carefully place the shaped cinnamon roll donuts into the oil, a few at a time. Fry them for about 2-3 minutes on each side, or until they are golden brown. Use a slotted spoon to flip them halfway through cooking.
Once cooked, remove the donuts from the oil and place them on a plate lined with paper towels to absorb excess oil. Allow them to cool slightly.
In a mixing bowl, combine the powdered sugar, milk, vanilla extract, and ground cinnamon (if using). Whisk until smooth and creamy. Adjust the consistency with more milk or powdered sugar as needed.
Once the donuts have cooled slightly, dip the tops into the glaze or drizzle the glaze over the donuts using a spoon.
