Carefully crack open a medium coconut; pour out the fresh coconut water.

Slice the coconut in half and chop the flesh into small pieces.

In a blender, combine coconut flesh, reserved coconut water, 4 cups water, sweetened condensed milk, evaporated milk, and vanilla extract. Blend until smooth.

Strain half of the mixture into a pitcher using a fine mesh strainer.

Add remaining 4 cups of water to the strained mixture, stirring well. Serve over ice.