Plan 5 day road trip

I don't know about 'thrilling' but my suggestion would be - if you are starting in Miami Beach you probably don't need suggestions for Florida, so on the first day drive to Savannah  You can spend time in Savannah or Fort Pulaski National Monument and then go on to Myrtle Beach where you can do the beach things.  For the next day go to Washington, DC (or Baltimore or any of the surrounding area).  There's something to interest most people in D.C.  And the last day you can go to Rochester (New York) or Niagara Falls (New York) or even West Point (New York)