Fulda is a nice place

When you want to see landscape than make a stop in the Rhön Mountains. A trip to the highest Mountain the Wasserkuppe with glider or Kreuzberg with a brewery and delicious beer is nice as well. When you want some german history make a stop on Point Alpha. This was a Cold War observation post between Rasdorf, Hesse and and Geisa, Thuringia. After that, when you need some recreation then I would visit the Keltenbad in Bad Salzungen (swimming pool with high sodium rate and sauna) Then I would visit Eisenach (Wartburg). And don't miss to visit Erfurt (although it is not on the route)

Meiningen in Thürigen is quite a nice city as well, worth a visit. And then, as already mentioned, Würzburg..

If you're staying strictly to your path of travel, then Wurzburg is the only city of size or consequence that you'll drive through. If you're taking Deutsche Bahn, then your route may be different. If you can extend past Suhl, then by all means see Erfurt, Eisenach or even Leipzig. I've been to the latter 2 twice, and thoroughly enjoyed both visits.

Do not miss the smaller cities like Erfurt or Eisenach. Erfurt has a very pretty city centre and Eisenach with the Wartburg is also worth visiting!

Depends how quick you want to get there. Wurzburg is right on the way to Suhl and is pretty interesting. If you want to take a more round about way you can go north to Erfurt or south to Nurnburg. Nurnburg is a little out of the way, but really worth the visit if you have the time. Erfurt is closer and also interesting.

Wurzberg is pretty nice if your into festivals, I think they are having one in the end of August for winegotten?