For many fruits and vegetables, the juice is what you obtain by crushing the fruit's flesh. Coconuts, however, are a completely different story. If you crush a coconut’s flesh to obtain a liquid, you will not have coconut juice, but rather coconut milk. A coconut’s juice is the almost clear, mildly sweet liquid that you can hear sloshing around when you shake a coconut. Obtaining this juice, also known as coconut water, does not involve crushing the hard flesh of a coconut in an attempt to extract liquid.
Examine your coconut carefully. Most of the outside should be consistently hard, brown and somewhat hairy. One end should be somewhat pointy. The other end should have three smooth, darkened dents. These may look somewhat like a face or the holes in a bowling ball.
Rinse the coconut under cool, running water. Scrub the dents and the area surrounding them. The coconut juice will come out of these dents, so cleaning the area around them will ensure that your juice is as clean as possible.
Hammer the nail through one of these holes. After hitting it with the hammer a few times, you should feel it slip easily inside. This means it has pierced the shell and flesh of the coconut. Remove the nail from this hole and pound it through each of the other two dents in turn.
Turn the coconut upside-down and rest it in one of your glasses. This will allow the juice to drain from the coconut into the glass. Leave the coconut there for as long as it takes for the juice to completely drain out. This may take five to ten minutes depending on the size of the holes you made and the amount of juice in the coconut.
Put the strainer in the top of the empty glass, then pour the coconut juice through the strainer into this new glass. This will remove any remaining bits of shell or coconut flesh that might be in the juice.
When choosing a coconut to juice, gently shake the coconuts and try to find the one that feels and sounds like it has the most juice inside. This is a sign that your coconut is fresh. You can use the coconut flesh after draining out the juice. Wrap the drained coconut in an old towel or put it in an old pillowcase. Hit it with your hammer until it breaks, then unwrap the pieces, separate the shell from the flesh, and use the coconut flesh in any way you wish.