I have a factory for an interface with different implementations. But one implementation needs an extra method which the others don't need. How do I solve this without implementing "not implemented exception" methods in other implementations?
Do the consumers of the inteface need to call the method that is only required for one implementation?
If the consumer does not need to call the method, it is an implementation detail. Therefore, it is not of interest to the consumers of the interface, as they even should/must not call it. Just add the method as a private method of the implementation that needs it.
If on the other hand the method must be accessible for the consumers of the interface, you are violating the Interface segregation and Liskov substitution principles. Extract the method in an own interface.