If you’re looking for a top of the line cooler that will keep everything cold for days on end check out the Yeti brand. If you’re a little more budget conscious there are cheaper competitors that are effective enough. One trick I like to use is to bring multiple coolers. One for the food items and one for drinks. That way your meal items do not warm up as you grab drinks throughout the day. Consider bringing food items that don’t need to be refrigerated at all: Avocado on your sandwich rather than mayo and cheese.
Don’t leave your cooler in the car or in direct sun. Find some shade and lift it off the ground by setting it on some logs or rocks.
Reduce and move food out of original containers into water-tight containers. That will save space, reduce food waste, and save the food from melted ice.