For our very long stopover in Moscow Sheremetyevo (yes 13h is very long) we were lucky enough to get a room at Capsule hotel “Vozdushny Express”, Terminal E. This is the only hotel inside this airport.
It’s really basic but it’s clean and trust me, having a private bathroom and a shower during long stopover is priceless.
If you have to stay in this airport for some time and are willing to pay a bit for comfort, this is definitely worth the money. The staff is nice and speaks English. Minimum stay is 4h. Price depends on the room type and how long you stay.