The recommended best practices for authenticating services in GKE to access Google Cloud APIs are to use Workload Identity. Enabling Workload Identity (option B) allows Kubernetes service accounts to impersonate Google Cloud service accounts, avoiding the use of static credentials. Binding the Kubernetes service account (KSA) to a Google service account (GSA) using IAM roles (option E) is the necessary step to establish this identity federation. Options C and D involve using service account keys, which are long-lived credentials and not recommended. Option A uses the node's service account, which is overly permissive and not workload-specific.