Germany for 2 days

First place, why are you renting a car and driving? Driving from Frankfurt to Munich takes longer (4¼ hrs by car per ViaMichelin) than going by train (3½ hrs, Bahn schedule). Fuel for a compact car costs over 50€ (also ViaMichelin), whereas, with advance purchase, you can do the trip for 29€. There's a lot of things to see in Munich when you get there, and some things to see in Frankfurt before you leave. Forget things in between; see the Frankfurt area when you get there, then go to Munich and see what's there. Most of the things to see in between Frankfurt and Munich can also be scheduled via trains, but if you have never been to either Frankfurt or Munich, spend your time there.

Agree with Lee 100%. You do not want to drive after a flight from L.A. -- especially if you've not driven in Frankfurt before. Keep it simply and stress free by taking the train.

After a flight from LA to Europe you're unfocused and tired even if you're flying Business Class. Use the time to be fit for the meeting on Monday. I've seen colleagues after such a trip who have fallen asleep repeatedly during the meeting.

Stay overnight in Frankfurt and head off to Munich the next day. This way you can go ahead and buy cheap train tickets now without needing to worry if your flight will be on time, plus you have the chance to do some sightseeing in one of Germany's' oldest, very important & historic cities. Yes, I am talking about Frankfurt. If you give us the date, I can tell you what fests are happening then.

Great information, thank you! the train it is. I will stay in Frankfurt through Saturday July 11 ( festivals?) and take train on Sunday to munich. What are the few cant miss things in Frankfurt?
On another subject , after my meetings for the week, i am taking the train from Munich tp Prague. Any opinions/advice for Prague?