Cheap fun late night ideas?

So I have this friend I want to hang out with but is always busy. I really busy too because I have work, school and everything else in between. After making some modification to my schedule I found that the only time we have free are nights. We are working on this project together right now but I am kind of getting tired of it. I want to take a break but with my limited schedule I don’t know what to do. I am on a budget so there are some things I just can’t do right now. I was wondering if you the readers would be interested in helping me out with a few ideas on what activity can be done at night with little money. What do you guys think I should do?