Great question! Check out my Instagram - I posted a video about this very thing haha I demonstrated how to use a low-hanging tree limb as a pullup bar - but if that's also not an option, you can grab the edge of a table and do inverted rows. You can do towel pull-ups - wrap a towel around both sides of a doorknob - place a towel or yoga mat underneath an open door to hold it in place. Use the ends of the towel to pull yourself in towards the edge of the door with a rowing motion. You can often find pullup bars are public parks. I hope these ideas help!
