For the purposes of a pun, "cans" are another word for "headphones".

Here's how to make audio-cans from soup-cans, and some other things.

Step 1: Parts & Tools

I used:

Two large soup cans (Lidl chicken, vegetable & pasta - it's OK)
One Scotch Broth can (Lidl, better than OK)
Two small speakers (4 Ohm)
A wire coat-hanger
Electrical insulating tape
Various bits of wire
Expanded polystyrene foam
PVC tube
Most of the electrical content came out of an old phone I bought a while ago.

Screwdrivers
A knife blade
A drill
Fencing pliers
Pliers
Scissors
A soldering iron

Step 2: Mounting the Speakers

I held the speakers in place with two blocks of expanded polystyrene foam.

Wash and dry the soup cans thoroughly.
Press the cans onto the foam to give you a rough size to cut.
Cut circles of foam, but trim ~ half an inch off two sides, you'll need this to get the foam into the cans (see later).
Press the speakers onto the foam to give you a rough size to cut.
Cut enclosures for the speakers, in this case the rectangular holes grip the magnet assemblies.
Taper a round edge to accommodate the speaker-cone, and ensure there's room for wire to pass through the foam block.

Step 3: Connecting the Cans

This bit involves the most hard work.

Untwist the coathanger and straighten it out as best you can.
Bend 2 x 90^o in the middle to give a square turn through 180^o.
At the ends of the wire, bend each around 90^o and trim (I had to use fencing pliers on this - it was tough stuff)
Form 90^o bends at each end, and curve the centre section to fit your head.

Run (electrical) wires across the the coathanger, securing with tape, these will connect one speaker to the audio input from the other can.
Whilst I was at it I incorporated two sweet-wrappers for reasons which should be obvious now if not later...

I've then secured the end pieces to the main cans with small sections of steel cut from another can.
Holes were drilled through both and the two pieces of metal connected with a pair of nuts & bolts.

Step 4: Final Assembly

Solder the wires together as the diagram..

A hole was drilled in the right can to take audio-in cable (from the phone, which conveniently had a screw-mount crimped onto the cable)

The black & white wires running between the two cans connect to left audio-in at the right can, to the speaker on the left can.

The right hand speaker connects to the right audio-in at the right can.

Once connected, wrap exposed joints with insulating tape and push the speakers in.
Because of the rim on the can, the foam must be pushed sideways (hence the need for trimmed edges) then rotated into place. It's a firm friction-fit.

A piece of PVC tubing was cut to fit the inner rims of both cans, cut lengthways it holds it's self in place no problem.

The other end of the curly phone cable was soldered to a standard stereo audio jack

Step 5: In Conclusion

These work fine from my PC, but they're not loud.
They are rather comfortable too, not that you'd expect it.
Running through a small amp makes them much louder, but as you might imagine, yes they do sound "tinny".