ADB sideload doesn't work, no drivers
I needed to edit the android-winusb.inf driver descriptor file for the Google USB driver. 


Add in the device hardware ID from Device manager under the Google Nexus(Generic) section for the unrecognized device connected in sideload mode as (for both the x86 and x64 sections):

%CompositeAdbInterface% = USB_Install, USB\VID_18D1&amp;PID_D001
%CompositeAdbInterface% = USB_Install, USB\VID_18D1&amp;PID_D002 

Switch off Windows Driver Signature Enforcement, 
Reboot, 
Add the modified USB driver manually to the listed device in Device manager,
Let it install the unsigned driver, and now it works.