I do not know which aircraft were capable of doing it, but I believe I've seen pics of quite some fighter planes with their canopies open during cruise flight(low altitude of course..

).
Would it not be fun if you can open up the canopy and throw the beercan over to your thirsty wingman

?
I see "door open" messages on a fighter plane when I press "O" key.. I dont seem to notice anything different happening though.. It may be quite some work to fix all those graphics and stuff so the canopy displayed shows opening/closing movements, I'll admit

.. and it's not an important thing and hardly worth the effort, too. O admit that also.
But, let's say...
Just for the fun of more delicate, subtle and immersive AH we know and love
Cheers!