My worst ones are chewing and sniffing. I have yet to find a solution for chewing other than blasting white noise directly into my ears during meals, but I actually have a trick for helping with sniffling.
Of course, headphones or removing yourself from the situation would be better but if both are entirely impossible then sometimes it can help if you pretend it’s actually the sound of paper ripping (unless that’s also a trigger, I guess. I’m kinda new, ahah).
If you can convince your brain that your sniffing neighbour is actually just tearing paper (if you can get into the right frame of mind, they’re remarkably similar sounds) then it reduces how annoying it is. If you have misokinesia and the person is in your eyeline, you’re out of luck.