Cargo jettison. It seems quite simple.
A bit tricky on a nose loader!
A bit tricky any way you might try to do it. Assuming we're not going to worry about weight and balance issues as the containers are tossed out the door, and hoping the person(s) pushing the cans don't get sucked out as well, you still have several issues to worry about.
The containers, when loaded, might be anywhere from a couple thousand up to twelve thousand pounds each. We have crews of people loading them on flat level ground so it would be difficult (to say the least) for a single person or two to push them out the door while the plane is in flight. Seems as if 400+ MPH winds buffeting against the doorway may add a bit of resistance too.
Then you have the rollers on the floor. If those get heated they're going to distort. Once they get distorted you're not going to be able to move anything on them.
And even if you were able to push the containers out, the doors are in front of the wing. If you manage to miss the wing I doubt you'd miss the horizontal or vertical stabilizers.
On most aircraft (in most common load configurations) the crew wouldn't be able to make it back to the door opening to begin with so that pretty much shoots the idea down right there.