Frankfurt recently enabled a T-mobile 30 minute free WiFi hotspot airport-wide. Once the 30 minutes pass, you are required to pay 5 euros for a full day of WiFi. However, there’s a way around it, at least for now.
Once you connect to the WiFi network (It’s called Telekom), you’ll be presented with the login page, which requires an email address from you. Just write your own for starters, then a 30 minute timer will appear and log you out exactly after 30 minutes. Here’s where the trick comes in - once you’re disconnected after the 30 minutes, open your browser’s cookie manager and delete all cookies associated with hotspot.t-mobile and telekom.de, then proceed to connect again, write out a random email address - presto.