P-38 is on the keyring at all times. Ya never know
And I don't like making my pocket knives into screwdrivers, as using them like that and you end up with the exact tool you were so desperately needing.
I do not have a P38 but if you poke the knife into the middle of the can and push down and pull to the side of the can it will cut easily.
make an X in the top of the can and peel the ears open.
Even easier and just about as fast is (if you have concreteslab or concrete block or or flagstone) rub the top of the can on a rock applying downward pressure.
Basically sanding the rim off. Your rock will get wet from the liquid in the can flowing out.
That is when you are almost done with the rubbing.
About 30 seconds and you can be into a can of goodies.