What to actually say
Open with this, more or less word for word: This is either the best cheese table I've seen at one of these, or I just haven't eaten since lunch.
I don't think we've met — I'm Sam, I do data work over at Bristlecone.
A name plus one concrete detail gives them something specific to respond to, instead of the vague 'what do you do' loop.
What made you come out to this one tonight?
It works on anyone in the room, whether they were dragged here by a boss or actually chose it, and it gets them talking about themselves fast.
So are you finding this one useful, or mostly here for the food like me?
Light self-deprecation gives them permission to admit they're bored too, which is usually true and instantly relaxing.
I'm going to go say hi to a couple more people before this wraps up — good talking with you.
It frames leaving as a task you have, not a verdict on them, so it doesn't read as rejection.
How it usually goes
A version of the conversation with the push-back left in, because that is the part you need to have already heard once.
What not to say
So, what do you do?
It's the first question everyone braces for at these things, and it puts the whole weight of the conversation on their answer being interesting.
I hate these things, don't you?
It forces them to either defend the event or agree with a stranger's complaint thirty seconds after meeting them.
Sorry to bother you, I just didn't know anyone else here.
It announces your nervousness and gives them a reason to see you as someone to manage rather than talk to.
If they keep talking after your exit line
Some people don't take the hint the first time, especially if they're also relieved to have someone to talk to. Don't repeat the same sentence louder — add movement. Say, "I'll let you finish that story next time I see you, I'm going to grab a refill," and actually start walking toward the bar as you say it. The physical move does the work the words alone won't. If they follow you, that's fine — you've just added a second stop to your circuit instead of being stuck at the first one.