You can usually see which laptops use 18650s, by the shape of the case. Pick a laptop, and search Amazon for replacement batteries.
I strip the 18650s out of laptops for other uses. It's just cheaper that way. It usually works out to about $1 for each 18650, including the occasional bad battery.
Thin squares, like the MacBook Pro have, are different. It's pretty obvious that an 18650 wouldn't fit in it.
Built in batteries are more likely to be flat square or rectangle types. You're SOL for replacing those with a pack of 18650s.
I only strip them down for their cells. I suppose if you're *real* careful, you could cut the case open, and be able to reseal it. There are temperature sensors inline, that you'll want to keep. and you'll need to solder the new ones together. They're typically spot welded. And, obviously, you'll need to keep the original control board. ... or just buy a replacement pack on Amazon or eBay. When the batteries die in the laptops I use, I don't try to remanufacture them. While I could do the parts cheap, the labor would exceed the cost of the replacement pack.
https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3F...