How do I socialize with my grad school cohort when I hate going out?

All of the other grad students in my cohort like to go out to bars and clubs on Friday/Saturday nights. I can't stand it. I don't drink or smoke, I don't know how to dance, it's too loud, the flashing lights are too much, and I'm terrified of drunk/high people. I get so overstimulated and uncomfortable and it makes my skin picking 10 times worse. I don't want to go, but it is generally the only way they like to interact with one another outside of class. I don't want to be left out while they all get closer to each other. I would suggest a different type of hangout, but I don't want to be seen as a killjoy and have them resent me. What do I do?