Hopefully some of the experts can share, a good travel tips thread could be helpful. One thought would be to use disposable neb cups? Depending on your risk tolerance either rinse really well with hot water and replace after several days or daily. I have seen many cruisers will cut up a new sponge and add a few drops of dish soap to bring to wash out cups and tumblers so this could be an option. You can rinse with bottled or filtered water as well. Enjoy the cruise.