from my pretty regular travel teaching seminars, etc what I’ve found is to pack some snacks including easy to bring things like Beef Jerky and Almonds to save yourself from airport/plane food (which has gotten much better though)
Also if the stay is extended going to the grocery store right away and stocking up on some simple things so not every meal is eating out can help.
As far as training the key is to just do something and not worry about the exact routine you were following. A lot can be accomplished with the hotel room gyms that have dumbbells up to 40lbs I try to get right off the plane and get a quick pump and some quick cardio. Find a gym that is CLOSE to where you are staying as that is going to be the key to actually following it. If there isn’t one do what you can in the hotel gym even 15-20 minutes of a quick circuit helps
Other things that help to bring with you are a few bands and a hip circle
It is hard to make progress while on the road but by doing a little extra work and forcing yourself to get up and move around you can at least maintain
Above all else though make sure to have FUN while on vacation and enjoy it and indulge a bit more along with relaxing as well. It is a good time to take a deload and come back to training fresh and rested