Rinse the rice in a strainer to remove excess starch. Drain thoroughly and transfer it to a heatproof, deep container. Break the cinnamon stick into pieces and add it to the rice. Pour in 2 cups of boiling water, making sure the rice is fully submerged. Cover with plastic wrap and let it soak for 4 hours or overnight.
Blend the soaked rice, water, and cinnamon stick until fully broken down. Strain the mixture into a pitcher.
Remove the green tops from the strawberries. Roughly cut them and blend with 4 cups of room-temperature water until smooth. Pour the strawberry mixture into the pitcher with the rice base.
Add the evaporated milk, sweetened condensed milk, whole milk, and vanilla extract. Stir to combine. Add sugar to taste, ensuring the condensed milk and sugar dissolve completely.
Serve the horchata over ice and top with diced strawberries.