The principle of relativity does not mean that all motion is relative. For that it requires an inertial frame of reference. In particular, it could allow the sun to move relative to the earth (although no scientist would ever take that seriously), but it does not allow us to say that the earth is not rotating. Sunrise and sunset is caused by the rotation of the earth and not by the sun’s movements.
To explain, we are all aware of centrifugal force – the outward force when spinning. (Think of the force that pushes you out when you make a quick turn while driving.) The earth’s rotation exerts a centrifugal force on us that pushes us away from the earth. Of course, gravity is much stronger and pulls us down toward earth. However, there is more centrifugal force when you are closer to the equater – and none when you are at the north pole. Thus, your apparent weight is lower at the equator than at the north pole – there’s nothing that relativity can do to stop this, and it shows that the earth is rotating.