As part of your pre-trip planning, the designated cook should do some food research. In foreign or far-flung destinations, don't count on finding all the familiar grocery items you'd find in your own local supermarket. Unlike in the U.S., in many parts of the world, markets sell only produce that is either locally grown or in season at the time, and many convenience foods we take for granted in U.S. stores simply aren't available. Search online for foods and recipes indigenous to your charter area; this will give you a good idea of the items that will be on local market shelves. To take it further, have a look at provisioning lists from bareboat companies based in the area. Most companies post these shopping lists online for people who elect to have the company provision the yacht for them. It's likely that area markets will stock the foods that are on those lists.
If you're sailing with people whose food preferences you don't know, ask your crewmates some basic questions before you do anything else, such as: Is there anything you absolutely hate or cannot eat? Are you a vegetarian? Do you eat red meat, or prefer only fish and chicken? Which soft drinks, beers and wines do you prefer? Do you drink coffee or tea?