So far, my husband and I have only used a regular cooler filled with ice to keep our food cold. We previously had a Coleman, but we've since upgraded to a "bear proof" and lockable cooler since we tend to camp in hungry bear territory. The advantages of this way of storing cold food is that these coolers don't use power and keep ice cold for at least 2-3 days depending on the outside air temperature. The disadvantages are that every 2-3 days we have to go hunting for ice which can sometimes run about $3-$7 a bag. On our next big trip, we are going to try to use dry ice. Another disadvantage to our particular teardrop design is that the galley does not have space for the cooler, so we have to keep it outside of the teardrop, and in bear territory, that means having to pack it away in the car at night or when we leave our site. All that lifting is hard on the back.
separate the food from the ice with a clear, plastic storage bin. We bring the bin into the house and fill it with our food and then carry it out to the cooler, place it inside and then pack the ice around it. The ice and the food stay separate and we can also use that clean ice for our margaritas.
Another tip I've seen from teardroppers is to line the sides and the top of your cooler with a reflective, insulation. These are sometimes called radiant barriers or bubble foil and are sold in rolls that you can cut to the size of your cooler.
Some teardroppers are lucky to have enough space in their galley to hold a small 12-volt cooler. These types of coolers can run off the teardrop or car battery or can be hooked up to a solar panel on the roof of the trailer. There is no need to buy ice and the cooler keeps food at a consistently 36 degree temperature. The disadvantage is that these types of coolers are pretty small (about 15-17 liters) and some food will need to be frozen or cooled before putting them into the 12-volt cooler. Also, if you are camping for a long time, you may need to have access to campground power to make sure your battery does not get drained.