There currently are a variety of options to travel by night train from Cologne (Germany) to Kufstein (Austria), taking approximately 8 hours: Namely the UEX 1301 and the UEX 1303. These lines are operated by UEX.
UEX (Urlaubs-Express) runs seasonal night trains and car-carrying trains between Germany and Austria.
Options range from seats and shared couchettes to private couchette compartments, sleeper compartments and connected sleeper cabins.
You can bring your car, but only between the car terminals, and you book the vehicle along with your ticket.
There is a free ski compartment. Drinks and snacks are available in the bistro on board.
Children with their own seat or bed pay a reduced fare.