Here’s how display the Service Account of a particular instance in Google Cloud.

<pre lang="bash">gcloud compute instances describe server-name \
--zone us-central1-c \
--project project-id \
--format="flattened(serviceAccounts[].email)"

Result is:

<pre lang="bash">serviceAccounts[0].email: service-account-name@project-id.iam.gserviceaccount.com