Rinse the rice under cold water until it runs clear.
Add the rinsed rice, 2 cups of water, cinnamon stick, vanilla, and blanched almonds to the Instant Pot.
Pressure Cook on High for 0 Minutes. After it is done, immediately release the pressure by flipping the valve.
Pour all the contents of the Instant Pot into a blender with 4 cups of additional water. Blend for 5 Minutes until smooth. If using a smaller or older blender, remove the cinnamon sticks and add 1 tbsp ground cinnamon.
After blending for 5 Minutes, add the sugar and blend on high for another minute until dissolved and incorporated. Strain through a fine mesh strainer.
Transfer the contents of the blender to a large mixing bowl. Dilute the horchata mixture with an additional 4 cups of cold water. Add more sugar to taste and serve over ice with a sprinkle of cinnamon.