If you've time to kill, this relaxed cafe is the answer. Anticafé doesn't charge for its drinks, rather you pay for the time you spend there – €4 for the first hour, then €4 for successive hours. With that you're free to hang out and do pretty much whatever – use the wi-fi, play board games, read on the sofa, drink…
You can BYO alcohol or there's a bar with free drinks (coffees and fruit juices) and snacks.