Although you'd have to pay (up to 5 people on one 18 euro ticket which is good until 6 a.m. next day if you miss your flight ), you could ride s-bahn lines S1 or S8 wherever they go; not restricted to city center. Maybe there's something interesting at the Besucherpark. (MUC is pretty much now my international MR destination of choice - so much that I've made some friends here amongst the locals.)