The coconut opening trick I have seen is to pierce the eyes with a sharp object, drain the liquid through the holes, then strike the eye end of the coconut against the ground (or hit with a hammer). One of the eyes is usually softer than the other two, and if you can get through that one you don't need to open all three.
I've even seen people do this with a ballpoint pen. I use the corkscrew on a Swiss Army knife for this. None of the other tools on a typical SAK would survive being smashed into the coconut, plus I'd probably cut myself