So I'm out camping, and I don't have a fridge, what are good ways to cool-down my food or drinks? I've tried mixing salt and water to create a endothermic reaction, but it didn't work too well. What are your tricks?
In the cowboy days, the people traveling through the western desert would carry canvas sacks which they would fill with water. The water would seep through the canvas very slowly, and wet the surface of the bag. Evaporative cooling would then keep the water cold (at least cooler).
You could try something similar if you are in a dry climate (the rate of evaporation determines the cooling effect, which is limited by the relative humidity). Wrap the food or drink in wet cloth, and hang or set in a shady location with some wind. Keep the wrapping wet.
If you're near a creek or a lake, usually just sticking your drinks in the water gets them well below the ambient air temp.
Besides what @KevinSelker said, if you have sand available : wrap the food tightly, cover in sand, then add water. You're looking for evaporative cooling, so the water doesn't have to be cool.
If you don't have that, and it's summer time, you can dig a deep hole, as the ground temperature will be near 65F if you get deep enough.
When I used to go camping, we'd bring some of the food frozen hard, so we'd not have to worry about it 'til it came time to cook it (eg, the next morning). (and then only relied on things that needed refrigeration for the 24hr or so, depending on the weather. (unless winter camping), and made sure to eat everything so we didn't have to worry about leftovers.
Get an old wool jumper (sweater), make it wet, wrap it around the container of food and place in the wind, keep wet, wool is best for this.
1If you can explain why using wool is better than the generic "cloth" in a previous answer, I'll be happy to upvote. Else I'll have to vote "delete" because it's nothing new.– Stephie ♦Dec 23, 2016 at 20:19