Build a quick full body session around the dumbbells, adjustable bench, and cable or machine that most hotel gyms have.
The quick answer
Most hotel gyms have adjustable dumbbells, a bench, a treadmill, and maybe one cable or machine, which is plenty for a solid full body session. Pick one move per pattern: goblet or split squats, dumbbell bench or push-ups, one-arm rows, shoulder press, and a core move. Do 3 sets each near failure and you will hold or even build muscle on the road.
How to think about it
Go full body with dumbbells
Since you likely only have a couple of gym visits per trip, train everything each session. Dumbbell bench press, one-arm rows, goblet squats, Romanian deadlifts, and shoulder press cover the whole body with one pair of adjustable dumbbells.
Push intensity to offset light loads
If the dumbbells max out lighter than you like, take sets closer to failure and add reps, tempo, or pauses. A set of 15 to 20 tough reps grows muscle just as well as a heavy set of 8 when you push near failure.
Use supersets to save time
Pair a push with a pull, like dumbbell bench with rows, and rest less between them. You keep the heart rate up, finish faster, and still hit every major muscle in 30 to 40 minutes.
Do this
Scan the room firstNote the dumbbell range, bench, and any cable or machine so you can plan around what is actually there.
Hit each movement patternCover a squat, a hinge, a horizontal push and pull, and a vertical press or pull.
Chase reps near failureWith capped weights, stop each set within a couple reps of failure to make light loads count.
Superset to beat the clockPair opposing muscles back to back to finish a full session quickly.