First, what are your normal "fitness" goals? That will effect what you can do, if anything. For instance, if it's a real strength program, you're probably screwed. Progressive overload is truly next to impossible with body weight and bands etc. And honestly I have seen a lot of shoulder issues with those who focused on body weight exercises like push ups during the shut down to a point that I think push ups, band exercises etc lead to more injuries and overuse issues than real barbell movements ever would give you. Heck, I have grown to believe push ups are a MASSIVE waste of time. They honestly weaken a strong athlete and hurt the ones that are not. The number 1 way to lose your squat and bench numbers are doing a bunch of body weight BS. These are things the commercial gym training world will probably lose their mind over, but it's really true.
If you are more of endurance athlete/"general fitness" as opposed to strength training or even hypertrophy training (body building/muscle growth) than I will say that if you do the body weight exercises with care and exact form and truly watching it b/c, again, it's dangerous, it's fine in moderation. Honestly, you might be better off just laying low and taking the hit as you are not going to become "unhealthy" in that short of a time and might be able to use the rest even. You'll lose some strength, but that better than hurting yourself trying to do something you are unfamiliar with while in a place that's not your normal place to train in. Sucks, but that's my advice. A few push ups and stuff are fine just do not over do it. Honestly, your conditioning can be done with a jump rope. Hell, I would just get that and do a bunch of jump rope circuits and build those up over time. 2-4 times a week. Obviously things like a battle rope or Concept 2 Rower would be AWESOME but probably not realistic in a hotel room but if you had access to their gym then they might (but doubt it) have those. Otherwise, simple things and eat whatever they give you. Look, it's Japan, doubt the "unhealthy" food is that unhealthy. Eat the rice (carbs aren't evil) and enjoy whatever you get.