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Even though a cooler is meant to keep everything cold, you can also use it to keep hot foods hot. Double-layer aluminum foil around the interior of the cooler. The aluminum will hold the heat inside your cooler. Lay out a large piece of aluminum foil on your counter and set your hot container onto it. Make sure your food is piping hot as you wrap the foil around it. Use a few pieces of foil to cover the container completely. Use an oven mitt as you wrap the foil so you don't burn yourself. Set the container in the middle of the cooler. The heat from the container will transfer through the aluminum foil and keep the entire cooler warm. Fill new cotton socks halfway with uncooked rice. Once you have the rice inside the sock, tie a simple knot on top so none of it spills out.  Use a string to tie the socks for added security. Dried beans will also work similarly. Use the regular settings on your microwave. Once they are finished, they will be nice and warm and they will hold heat for a while. Fill in the large spaces on each side of your food container. This will add more heat to the cooler and help your food stay at a reasonable temperature. Use clean towels so your food doesn't move around while you transport it. Make sure the towels are tight against your food so they insulate the heat inside. Fill a rubber hot water bottle with boiling water. It's easiest to pour the water into the bottle from a kettle or a pot with a spout. Place the hot water bottle on top of the cooler for one final heating element to keep your food warm. Seal the lid of the cooler tight after you add the water bottle so no heat can escape. The temperature of the cooler will start to drop over time. Carry a food thermometer with you to check on the temperature of your food to make sure it is above 140 °F (60 °C).
Line the inside of a cooler with aluminum foil. Wrap your container of hot food with another piece of foil. Place the container inside the cooler. Make 2 or 3 heat packs by filling new socks with uncooked rice. Microwave the heat packs for 2 to 3 minutes. Place the heat packs on the sides of your food container. Fill in any gaps in the cooler with towels. Put a hot water bottle on top of the towels. Eat the food within 2 hours.