These! I got these today, and they WORK! The small ones work in the 18490s, and the middle size works in the Woodvil and Grands. They're very soft and easy to squonk, and the hole in the cap is easy-peasy. Like QUIGSWORTH says.....don't over-think it. The cap is made of soft plastic, so just stab it to get it started then ream it out with a scissor blade.
They hold more, are easier to squonk, and they look cool. In the Woodvil 18650 I can't even see my battery anymore. It just looks like a flat piece of plastic with juice behind it. They are great so far. Also, the cap seals very well, so no o-rings needed. All in all, IMHO they are definitely a win.
There are three sizes in the package....11 bottles altogether (4 little ones, 4 medium ones, and 3 big ones (that don't fit our purposes but will work for something else...??

)....all for $4.99 and free shipping. I recommend. So far I've switched out one Woodvil, one 18490 Woodvil, and one Mini 2.1. This is my afternoon project......right after I put in another order for a few more.
Also, you'll have to re-learn squonking because it takes a lot less effort to squonk these...less pressure and less time.