There are many ways to open these young coconuts. The following method is great if you are opening a coconut for the first time. You will need a cutting board and a cleaver.
holding the coconut firmly on its side, make five or six slices in the husk with the cleaver held at a 45 degree angle pointing towards the point of the coconut. rotate the coconut for each cut.
the entire point of the husk should come off in a flower shaped piece. You may need to remove a little more at the end to expose the tip of the coconut shell.
hold the coconut firmly on its side and sharply whack the tip with the cleaver about 1/2 an inch from the end. as soon as you enter the shell, try to turn the coconut upright so not to lose the precious water. pry off the rest of the tip using the cleaver.
at this point, drink the water with a straw or empty it into a container for use in recipes. you may have very thick meat at the tip, in which case you must pierce the meat to empty the water.
after emptying the water, return coconut to its side and firmly hold it while making a slice with the cleaver starting at the cut edge,but now hold the cleaver at a slight angle leaning into the coconut. rotate the coconut as you cut. this will open a larger hole so the meat can be easily removed.
use a spoon to scoop out all the meat. I usually get between 3/4 and 1 cup of meat.
many times the meat can be pulled out by hand if you can get a finger between the shell and the meat:)
There are many videos (on you-tube) about the opening of these coconuts , and this site offers a similar method. Here is a site that uses a knife.
My favorite way to enjoy young coconuts is just as they are! Drink the water, and simply eat the meat. Sometimes I include them in smoothies, or make a simple pudding/yogurt by blending the meat of 1 coconut with the juice and zest of 1 organic lemon, any sweetener like soft dates or agave, the seeds from 1 or 2 inches of a vanilla bean, and a tablespoon of coconut oil. This is a non-cultured yogurt, however I believe it can be cultured by adding the powder from a probiotic capsule as described in this link.