Sulfites are chemicals that are commonly used as preservatives for a range of different types of foods and beverages. For example, sulfites are often added to shellfish to prevent discoloring, processed foods to give them a longer shelf-life, and dehydrated fruits and veggies to preserve them.You can also find these chemicals in soft drinks and alcoholic beverages like beer and wine.or example, sulfites are often added to shellfish to prevent discoloring, processed foods to give them a longer shelf-life, and dehydrated fruits and veggies to preserve them. You can also find these chemicals in soft drinks and alcoholic beverages like beer and wine.