I suggest not using Sprites directy, but instead turn to scene2d and its Actors. The libgdx wiki already perfectly describes how to do this then.
You would create a class that extends Actor (or Group) and that renders the texture you want.
When creating your box2d bodies, you would set the bodies' user data to the actor via setUserData(actor);
Now after simulating the box2d world with step(), you just need to iterate over the bodies in the world, access the actor through getUserData()
and update the actor's position and rotatin to the current values of the body. The wiki already contains the complete loop needed for this...
Hope it helps... :)