In a bowl, soak your cashew nuts with water and leave it covered for at least 6 hours or overnight, preferrably.
Drain the water and rinse. Then transfer the cashews in a blender. Pour about 3 cups of filtered water. You can add less water if you want it creamier. Add a pinch of salt if using.
Blend on high speed for at least one minute. Then transfer to a clean and dry glass container. Add a cinnamon stick if using. Cover with lid and store in the fridge for up to 4 days.
Notes
Homemade nut milk will tend to separate. So just use a spoon to stir it prior using.