OeBB Austrian Railways have reinvigorated the overnight sleeper train train market in Europe and other operators are putting a toe in the water.
Alpen-Sylt-Nachtexpress
The private Alpen-Sylt-Nachtexpress
runs overnight twice weekly in each direction in summer from and to
Westerland, Sylt via Hamburg, Frankfurt and Munich to Salzburg.
(https://www.nachtexpress.de in German. Use a translator app.) The Alpen-Sylt-Night Express is
made up of 10 couchette carriages (including a special carriage for
people with disabilities or reduced mobility) and the locomotive with
sufficient room for baggage. The train team is present on board for information and service. I suspect the trains may well take tandems and trikes. The list of baggage carried is long and comprehensive:
Prams, Strollers // yes and free of charge
Wheelchair // yes and free of charge
Rollator (wheeled walking frame)// yes and free of charge
Kiteboard // yes and for a fee
Surfboard // yes and for a fee
Stand Up Paddle Boards// yes, if it is in a bag and for a fee
Foldable canoes // yes and for a fee
Sunshades / beach umbrellas of normal size // yes and for a fee
Bicycle // yes, as long as space is available and for a fee
Wheelchair // yes and free of charge
Rollator (wheeled walking frame)// yes and free of charge
Kiteboard // yes and for a fee
Surfboard // yes and for a fee
Stand Up Paddle Boards// yes, if it is in a bag and for a fee
Foldable canoes // yes and for a fee
Sunshades / beach umbrellas of normal size // yes and for a fee
Bicycle // yes, as long as space is available and for a fee
Just to make sure I will drop the operator a line to enquire and report back.