I confirm rsh913´s suggestion !
It´s the most viable solution.
Although Memmingen Airport is the nearest it´s useless because X3 is the only airline serving this airport and they only have a single flight on sundays late in the evening. (next to the fare being already rather high)

If you book a trainticket (i recommend doing that as soon as possible as cheap tickets are sold out fast - in particular for sunday travels ! ) you´ll get by far the best price for your journey!!! And the "Deutsche Bahn" gets you there relatively fast. (you will have to change trains at least once - at Augsburg or München/Munich Hauptbahnhof i´d expect - )

Just check out http://www.bahn.de/international/view/en/index.shtml

They even show the schedule including bus services to your final destination (although the train ticket does not cover the bus sectors !!!)

Another solution is to fly Berlin-München (there´s Air Berlin next to Lufthansa) which probably may save you 1-2 hrs in total journey time if continuing by train from Munich airport (there´s a train station inside Munich airport ! )