I could not find any examples of this existing for Europe (there seem to be some hotel and hostel passes in NZ and Aus). I tried generic serach terms, and also dug around the websites of: Marriot, Hilton, Accor, Ibis, Best Western, HostelingInternational, HostelWorld, Generator Hostels, Wombat hostels. I could see nothing even resembling this there.
While not quite what you want, about the closest that seems to exist are equivilants for camping:
Other than that your best options seem to be making on-the-day bookings with the likes of LastMinute’s "Top Secret" scheme, or LateRooms, or showing up to local tourist information centres (which can be of mixed use). None of these are quite as convenient as what you want.
To the best of my knowledge such a pass does not exist for Europe as of now. This does not exclude its existence, but it is highly unlikely. Furthermore I doubt you would be able to make significant savings if there were such a pass, compared to careful price shopping.
Why I don’t believe it exists
What can I do to replicate the flexibility of such a pass
Honestly, initially I thought such a pass does not exist, as has been pointed out in comments by @ZachLipton
Hotels also use demand-based pricing to a much greater extent than trains. Hotel rates vary significantly depending on the market, the season, events in the hotel or around the city, occupancy levels, and other factors. A hotel chain wouldn’t want to lock themselves into a single rate for all of Europe, as it would eliminate their flexibility to, say, charge a vastly increased rate if a major convention is taking up every bed in town.
However I did find such a pass e.g. for New Zealand. I did not on the other hand compare their pricing and I doubt you are making the best deal in terms of hotel quality and pricing compared to researching hotels and prices for every city without restricting yourself to one hotel chain.
Credit:stackoverflow.com‘