Applying ansible playbook to a docker container on a remote host
With the help of @Levi (refered to Stackoverflow) I managed to find a way to connect straigt into the docker containers using ansibles docker connection driver and the remote API capability of Docker. 

First of all you have to expose the API which is by default not the case. Simply add -H tcp://0.0.0.0:1337 to the ExecStart constant of the systemd script. Then reload the start script and restart the docker service. (From this blogpost) 

Then you can list the containers in the inventory file like this:

[containers]
container-name ansible_connection=docker ansible_docker_extra_args="-H tcp://1.2.3.4:1337"


And execute any playbook like your used to.

ansible-playbook -i docker_inventory playbooks/my_playbook.yml


The upside of this way of implementing it this way is that you can mix up "real" hosts/vms that are maintained through SSH and Docker containers. One negative thing I have to mention is that the docker API is much slower than using SSH as a control tunnel.

This setup is of cause horribly insecure and its only purpose is to explain the concept. Before using it in production you should read into the security features and limit access to the daemon as far as possible.