Which is the cheapest way to reach Berlin from Frankfurt airport?

The cheapest way to reach Berlin from Frankfurt airport is by train. The Deutsche Bahn (German Rail) operates several trains per hour between Frankfurt and Berlin, with one-way fares starting at around €20. The journey takes approximately 4 hours. Another option is to take a bus, with fares starting at around €10, but the journey time can be longer, up to 6 hours.