Combine the rolled oats, milk, honey, and cinnamon in a mixing bowl, whisking until the mixture is smooth and the honey is dissolved.
Pour the mixture into a jar or airtight container, smoothing out the surface with a spoon.
In a small bowl, stir together the cinnamon sugar or extra cinnamon to create a swirl topping.
Dollop or drizzle the cinnamon sugar mixture over the oats, then use a toothpick or the back of a spoon to create a swirl pattern through the mixture.
Seal the container and place it in the refrigerator overnight or for at least 4 hours to allow the oats to soak up the flavors.
Once ready to serve, remove the oats from the fridge and give them a gentle stir if desired.
Enjoy the creamy, cinnamon-scented oats directly from the jar or transfer to a bowl, adding extra toppings like fresh fruit or nuts if desired.