This, based on my emacs docker, is a docker that starts an emacs daemon.
The daemon is pre-configured with a shared key and to listen on TCP port 6001. So it's possible to connect into it.
It's not possible to make a frame outside the docker. But it is possible to eval stuff inside the emacs:
emacsclient -f serverauthfile -e '(+ 3 4)'
if serverfile contains the correct tcp and auth stuff.