kubectl top nodes command gives only CPU and Memory usage, how to get GPU usage information in Kubernetes cluster?
I'm afraid that kubectl top does not provide GPU metrics, regardless if drivers are installed or not.
To inspect GPU statistics, I recommend using Heapster monitoring tooland Prometheus that provides the extension to get the accelerator metrics.
At last, you may be interested in Nvidia GPU works for Kubernetes and GCE concepts of using this kind of hardware.