1. Combine rice, sugar & cinnamon stick in a large bowl.
2. Pour water over mixture; let cool to room temperature.
3. Cover and let the mixture soak for 3-4 hours or overnight.
4. Uncover & stir.
5. Pour mixture into fine mesh sieve over another bowl, saving both the solids and the liquid.
6. Scrape solids into blender with enough liquid to cover; blend until smooth. Add in the remainder of the liquid and blend until smooth.
7. Pour mixture into fine mesh sieve over another bowl or pitcher. Press the mixture in the sieve to extract all the liquid, discard any solids left in sieve.
8. Stir in evaporated milk.
9. Pour over ice and garnish with cinnamon.