Kubernetes Pods vs Deployments in Google Cloud

Based on your description, I would suggest you use a Deployment with replicas set to 1. The Deployment will ensure that there is always one instance of your pod running. You can define your environment variables in the pod template spec of your Deployment manifest.

In the documentation, you might also see suggestions to use replication controllers for the same purpose. This is definitely an option but Deployments are considered the successor to replication controllers and are usually recommended at this point.

A bare pod is not intended to be durable and will not be restarted in the case of a node failure or other type of eviction.

The documentation is out-of-date in many places but, as far as I know, the authoritative location (even for GKE) is http://kubernetes.io/docs/.