Add rice, cinnamon, and almonds to a bowl. Cover ingredients with water (about 1 1/2 cups). Let soak for at least 5 hours or overnight, until the rice has slightly softened.
Using a fine mesh strainer, strain the water from the cinnamon, rice and almond mixture. Pour the strained mixture into a blender, and dispose of the water.
Blend the cinnamon, rice, and almond mixture along with the evaporated milk. Blend until the mixture is smooth and the grains of rice are finely ground.
Strain the liquid through a fine mesh strainer into a pitcher. Add the sugar, vanilla, and milk, stirring until combined. Pour in the 4 cups of water. Serve with ice and a dash of cinnamon.
Adapated from My Latina Table.