Combine oatmeal and water in a large bowl. Soak oatmeal for at least 10 minutes.
Place oatmeal in a blender along with naranjilla pulp. Blend for 1 minute.
Pour about 9 cups of water in a large pot. Stir in blended mixture, piloncillo and cinnamon sticks.
Cover pot and bring the mixture to a slow simmer for about 15 minutes.
Strain mixture, using a fine mesh strainer.
Serve hot or cold.