Hot thick cinnamon based drinks are very popular in Mexican cuisine especially in winter. There are many different types and varieties typically these aren't found in food places because they are considered a very "home-style" the only thing people might usually find outside is "Atole de Maizena", "Atole de Maiz", "Atole de Chocolate" etc.
-¾ cup plain Oatmeal
-2 cups whole milk
-8 cups water
-3 cinnamon sticks
-½- 1 cup sugar (sugar is to taste it depends how sweet you like it.
-¼ cup cold or room temp. water.
-Bring 8 cups of water to a boil on medium high to high heat. with 3 cinnamon sticks, when the water becomes brownish red shock it with ¼ cup water to stop boiling and let it come back to a boil this will cause it to get more dark red.
-Put oatmeal in a blender with milk and blend on high until smooth and oatmeal is almost destroyed kinda powdered., it's okay to have some pieces but destroy it as much as possible.
-Add to the boiling cinnamon water and stir constantly not letting it stick to the bottom until liquid starts coming to a boil and becomes creamy and starts to rise immediately lower heat to low and add sugar to taste stir to dissolve sugar and you are done.