4, but we didn't sleep, just fucked, if that's what you mean.
I've had sex with more than 4 guys at once in a bathhouse, but I don't think that should count, becomes more like a scrimmage than sex. And of course you can't really "sleep" in a bathhouse, if your term has several meanings.
Frankly, for me a 3-some is better. In my experience 4-somes tend to be difficult to manage & sustain, generally breaking down into 2 couples.
Also, one of my worst sexual experiences was a 4-some. My BF & I got invited to a couple's house, and all got naked. But these guys were both size queens, and started fighting over who would get me, which didn't do my BF any good.
Then one of them got jealous because I was paying more attention to the other, and started throwing hissy fits, and slamming doors all dramatically (the 3rd time he slammed the same door in 2 minutes got to be a bit much, but very funny looking with him naked).
We got out of there quickly, and not surprisingly this couple broke up a few months later. I've been wary of 4-somes with couples ever since. I suspect most of the couples who want to do it are less stable than the average, and I don't wanna be involved with that.