Operating a fan on UPS
A UPS as I understand it is an battery attached to an inverter. I have used portable fans on an inverter with no issues. Assuming they are designed for the same frequency. If you have a AC motor designed for 60 Hz and a inverter operating at 50 Hz it would just alter the speed of rotation. 

One thing I don't recommend is plugging an electric digital clock into an inverter because a minute will pass every 30 seconds or so. If your laptop is OK with it then your fan will tolerate it OK.