How the host can share data with the containers

On each build I would like to generate(on the host machine) a certificate and share it with that container. Any idea how could I do that?
Using the certificate the container could authenticate itself with external services. This increases the security and simplify the management as the certificates are short lived.

I’m looking for something like Volumes except they should “virtual”/created on and specific to each build. (e.g. /Volumes/ ) . Before the Volume mounted the host should also run a specific defined script/plugin (i.e. generate a certificate issued to the repo or build link).