When packing school lunches or your lunch for the office, use an insulated lunch pack or box. Brown bags don't work well because they aren't insulated and can become soggy. The Food and Drug Administration (FDA) recommends using freezer gel packs or small frozen juice packs to keep foods cold. The gel packs will keep foods cold until lunchtime, but won't work for all-day storage, the FDA says. Any food left over after lunch that can't be refrigerated should be discarded.