Recovering admin credentials

We have taken control of something that was developed by a vendor. For reasons I won’t go into, we have not gotten the admin credentials of the kubernetes cluster. I would like to avoid having to rebuild everything if possible since we don’t know how things are configured yet. I would like to recover the admin credentials if possible. I should have root access to the servers it is deployed on soon. But, I have no idea where to begin.

Does anyone have any suggestions? Thanks in advance for your help,