If you can grab a rag or similar object, muffle the top of the can and press down over that spot where the "mouth hole" is with the rag-hand as you pop the tab with the other. Try and make the rag-hand have no air gaps. In very quiet environments you will still be heard but should lower the volume a bit!
Use the tab to crack the pressure and once settled, start working around the initial rip with a flat tip screwdriver. Works well enough to hide beer from your parents, but is a lot of effort to mask it in a meeting at which point the attention you lost outweighs the insignificant disruption it'd cause everyone else
Perhaps more involved than you'd like, but you can get a "beer can cutter" which will allow you to eliminate the noise by removing the entire lid. Basically a fancy can opener.
You can also top a regular soda or beer can with one of those folding P-38 or P-51 style ration can openers. Jury's out on whether or not you'll get sprayed in the face when you first piece the can, though.
Yes. Raise the tab just enough to equalise the pressure, then use your thumb to slowly open the can hole, working from one side to the other. This video gives a tutorial using a beer, but it'll work for any aluminum drink can.
Get a heavy blanket or jacket or something similar, and open it underneath.
That said, if you’re trying to hide drinking beer from the parents… anything trying to hide it is just going to attract more attention than simply cracking it open
Quietist way with no extra equipment is to press your thumb to the tab that goes down into the can, wouldn't be what I call stealth but cuts the noise dramatically.
If you can, place it on a relatively flat surface and move it in a circle for a minute or two. Not sure of how it works, but I've opened cans with nary a hiss using this method. I've even managed to do it with the can just on my thigh and trying to keep it as perpendicular as possible.
Very slowly pull the tab so it just ever so slightly breaks the seal, so the gas escapes slowly, then use your finger to push the rest of the can open so it doesn't make that super loud "cracking open" sound.
Just be aware with this technique that going to the ER to patch up your sliced open finger is probably more distracting than the sound of the can opening.