Youtube, being the melting pot of useful hacks and DIY tutorials has the answer you might need for this. ‘The Crazy Russian Hacker’ channel presents an ingenious, hands-on way of cracking your can open. And by hands-on we mean, literally! How, you might ask? You don’t need to master karate, just rub the top of the can over a rough but horizontal surface. Then turn it the right way up, and press on the sides – the lid should open up. If it doesn’t work on the first go, try the rubbing part again!
The next video assumes you have a spoon at hand. That’s reasonable if you’re only missing the can opener. Make sure you try this one out as well: