Place the jasmine rice and Ceylon cinnamon sticks in a large bowl or container.

Pour 500 ml water over the rice until it is fully covered.

Cover the container and soak the rice mixture overnight, ideally for 8 to 12 hours.

Transfer the soaked rice, soaking water, and cinnamon sticks to a blender.

Blend briefly until the rice is broken down but the mixture is not completely smooth.

Strain the blended mixture through a fine sieve into a saucepan.

Add 4 tablespoons granulated sugar and 500 ml plant milk to the saucepan.

Stir the horchata until the sugar is dissolved.

Gently heat the horchata over low to medium heat until warm, without boiling.

Serve warm immediately, or cool and refrigerate in a sealed container.