There currently are a variety of options to travel by night train from Bonn (Germany) to Bischofshofen (Austria), taking approximately 10 hours: Namely the UEX 1311 and the UEX 1313. These lines are operated by UEX.
UEX (Urlaubs-Express) operates seasonal night trains, including car-carrying trains (Autoreisezüge), from Germany to Austria and back.
You can choose a seat, a couchette berth, a whole couchette compartment, a private sleeper compartment or connected sleeper cabins.
You can bring your car, but only between the car terminals, and you book the vehicle along with your ticket.
Skis travel free in the ski compartment. A bistro on board sells drinks and snacks.
There is a reduced fare for children who have their own seat or bed.