Place the rice and cinnamon stick in a bowl and pour the boiling water over it. Let soak overnight or for about 12 hours.
Place the rice, cinnamon, and water in a blender and blend until smooth. Pour mixture through a fine mesh sieve lined with several layers of cheesecloth. Pour strained liquid into a pitcher and mix with the coconut water.
Place the coconut milk in a saucepan along with the sugar and salt. Whisk together and heat just until the milk begins to steam. Remove from heat and pour into the pitcher with the rice/cinnamon liquid. Stir together and refrigerate until cold.
Serve on top of ice with a grating of fresh cinnamon and a lime wedge. Add cinnamon sticks to the glasses, if desired.
*make sure to stir the Horchata well as it will settle and separate. This is normal.
Recipe by The Kitchen McCabe at https://www.thekitchenmccabe.com/2015/05/04/coconut-horchata/