these days its best to be careful – employment law is now saying a works do is an extension of the workplace so everything you say and do can be held against you if something went wrong. (the excesses of the 80s and dot-com days have come to haunt us!)
most workplace dos are held in public places where other citizens are present and they can often work out where your employer is by listening in on conversations, you just don’t know who else is there – commercial rivals, office rivals, journalists, off-duty cops etc…
I just drink less and say “I am trying to look after my health these days” (which is actually true in my case – at least during the week!) – you could always say you have been feeling unwell and don’t want to drink too much, there are plenty of winter lurgis about.. with companies always wishing to drive down sickness absence levels, no one can fault you for wanting to look after yourself!
there are other opportunities to socialise at real parties where you don’t have to be worried.
had my works do today and was on my best behaviour – got plenty other opportunities to “misbehave” at the weekend raaa