Not sure if it's 'cheating' but I often see FAs giving premium class food and drinks to non-revs in Y or other goodies like amenity kits/blankets.
It is cheating and inappropriate and anyone caught doing it should be suspended.
Furthermore, anyone caught rigging the upgrade list to clear nonrev coworkers, friends, family or other-airline non-revs should be terminated immediately. Clearing of the upgrade list is not difficult to police and audit.
I don't have a problem with UA firing employees who sell passes, but anyone dumb enough to pay for what they know is a standby pass with an expectation that it's a confirmed space ticket, first class or not, is an idiot. If the employee is somehow modifying the document they are giving buyers or purposely misrepresenting it it to buyers, they should be charged with criminal fraud.