There’s discussion on /r/spacex that two Starships could be teathered nose to nose and set in a rotation during their ballistic flight to Mars, in order to provide at least Martian (~.3g) level artificial gravity along the way.

This is important because even things like convection in the air stop working well at 0g, so for example, you can suffocate on your own CO2 if you fall asleep and there isn’t a fan running.

Funny enough the hardest part about this doesn’t even seem to be the tethering or rotation, but two things; 1) you have to make slight course corrections along the way because the initial burn is never precisely accurate enough to target something as far away as a planet, and 2) occasionally you have to put as much mass as possible between you and the sun due to solar storms spewing radiation, so you have to stop the rotation occasionally to point the engines sunward to use your fuel as a radiation shield, or to course correct.