It's becoming impossible to train in an apartment

I've had my puppy before we moved to this apartment, and it's been a nightmare managing his reactivity. There are dogs everywhere, at any time, and it's not possible to always avoid them. Especially in the hallways, we have other neighbors with their dogs too and I need to always constantly worry about their dogs. My dog is reactive towards other dogs because he wants to greet them. But even with regular treats, he's refusing it and instead cares more about the outdoors. I cannot avoid other dogs, it's impossible. I live in a highly dense urban city and my only real option is to move to a quieter area to manage my Dog, or re-home.