After my experience with hoteliers opening room doors at night, I opted to always travel with a stainless cup.
You know that 555 cup with a hand? That’s right.
The plan is to hang it on the door handle. The cup falls off when someone turns the door handle from outside the room and it will wake me up.
That’s my local approach.
I came upon this internal door lock. It’s small and easy to travel with.
Travel Internal door lock
Travel Internal door lock

 

Also, you can learn how this meal storage tip can help you stay organized.