Have you looked at ConfigMaps? They're a newer feature of Kubernetes that is meant for storing non-secrets, but in general works pretty similarly to how secrets work (create config map, mount in container).
configMaps is nice, but we use it in limited way because its so much easier to update pods when editing env vars. Note: we are using deployments, so if you need to change env var, you do `kubectl edit deployment <name>`, edit/save/close file that opened in your $EDITOR and watch the magic to happen.