All you need is a sort of flat rock and the can opens cleanly after some rubbing.
This method is so simple, it’s silly. Take three minutes to learn the trick for the next time you forget your Leatherman. To get right to business, jump ahead to about 1:05.
Can Opening Tutorial In Text
The video shows how simple it is to compromise the seal on the top of a can. The hard metal sides along the top of the can wear down easily with an abrasive rock to reveal a much thinner and weaker seal which then is pushed open by squeezing the can.
Whether you own a can opener or not I think it’s worth trying.