To delete a Secret, simply use the kubectl delete secret command:

# kubectl delete secret access-token
secret "access-token" deleted

If a Secret is deleted when a Secret volume is attached, it'll show an error message whenever the volume reference disappears:

# kubectl describe pods secret-example-volume
...
Events:
  Warning FailedMount 53s (x8 over 1m) kubelet, minikube MountVolume.SetUp failed for volume "secret-volume" : secrets "access-token" not found