Get a train from Donny to Hessle, then walk over the Humber Bridge, take the train from Barton to Habrough and return to Donny that way.
Hull is not one of the least attractive places in the country BTW, as someone claimed upthread. It has some seriously splendid Victorian architecture (not least the north side of Alfred Gelder Street, which is just one enormous long building, presumably once a shipping office of some kind). Near the Wilberforce Museum (interesting in its own right and free) is a beautiful square of tall buildings with Dutch gables, dominated by an enormous church. If you were transported there in a teleporter you would think you were in Haarlem or Leiden or somewhere. The city has some of the most attrative pubs I've ever seen. Tiny little snug places, with exquisite tile work on the outside, often reached down little lanes that are even better than those in York because they aren't sanitised for tourists.