If you are trying to setup Always On availability group between SQL instances deployed as SQL containers on Kubernetes platform, then I hope that this blog provides you the required reference to successfully setup the environment.
By end of this blog, we should have three SQL Server instances deployed on the Kubernetes aka k8s cluster. With Always On availability group configured amongst the three SQL Server instances in Read scale mode. We will also have the READ_WRITE_ROUTING_URL setup to provide read/write connection redirection.
Refer Use read-scale with availability groups – SQL Server Always On | Microsoft