Pack resealable sandwich bags of a few different sizes. You never know what you are going to buy or encounter. I like bringing extra bags in case I buy something liquid. Since most liquids have to go in your checked luggage and you have no control over how it is handled or placed (upright, on it’s side). I seal anything that could leak in baggies. This way the perfume or cologne you pack in your bag and check-in won’t make you the talk of the trip by making you reek if it leaks. I also use the bags to store my swimsuit if it is still wet, make sure to take it out asap though so it doesn’t molder.