When doing outdoor sports like hiking or biking I'll always take a lot of cold water with me. I love to drink cold water and I feel more refreshed compared to drinking warm or not-so-cold water. But when the weather is really hot, I have a problem. I can't keep the water cool the whole day.

I tried various techniques like trying to isolate the bottles in towels or dedicated water coolers that you can buy in supermarkets. But nothing worked for the whole day. So what is the best option to keep water cool a whole day? I should add that I only use PET bottles.

8 Answers 8


In dry climates you can take advantage of evaporative cooling - especially on a bike. In hot and humid places you are stuck with insulation and pre-cooled water and/or ice.

Have you experimented to see if a cloth wrapper around your bottles is enough to cool things when damp? Of course, you're not going to get highly chilled water, but it can be refreshingly cool with just a little time and breeze.

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    Some canteens have a felt cover on them that is designed for exactly that purpose. You moisten it periodically, and the evaporation will keep your water cool. Commented Feb 1, 2012 at 3:27

Freeze the bottles, then keep them together if possible. Any insulation around them will help.

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    This works well, but be careful to freeze in a way that doesn't cause your container to burst.
    – D. Lambert
    Commented Feb 1, 2012 at 18:32
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    I freeze half-full bottles on their sides with the lid off - being on a slight angle from flat if necessary to keep the water from spilling out. Then in the morning top up with water. You can drink right away with this approach and it stays cold for most of the day. Commented Nov 27, 2012 at 22:17

If you're hiking in dry, hot weather places, and you have a whole backpacking setup your best bet is to store your water deep in your pack. The sun is your only real enemy here.

In the desert, I've had success with packing my bag so that my water is "wrapped" in my insulated gear - jacket and sleeping bag. Since I don't actually want to expose my sleeping bag to the possibility of a water spill (desert nights are still darn cold!), I usually put the water against the small of my back, and the sleeping bag in it's compression bag on top. Then I wrap my jacket around the front/bottom of the water. Pack the rest of your bag as best as possible around those items (it will be less comfortable and carry more awkwardly for sure). This way, the sun beats down on your sleeping bag and warms the top of it significantly. It insulates the water from that heat.

At night, leave your water out on the ground and make sure you pack it in the morning before the sun gets up. You will have the coolest water possible :)


This doesn't directly answer your question and might not be to your liking, but it's what I do.

Basically, I don't bother trying to keep it cold. However, I do add flavoring. I find that flavoring helps a great deal in making it feel a lot more OK to drink warm liquid. Think of it sortof like tea if that helps. Actually I don't add the flavoring for that purpose, it comes along for the ride.

Most of the the time, and always in warm or hot conditions, I add gatorade powder to the water. When hiking in the desert, it is essential to not only replace water lost, but also electrolytes. Don't mix the gatorade quite full strength, somewhere about 1/2 or 2/3 strength seems to be best.

When you're hiking in the desert, everything gets hot. Trying to fight that will only cost you extra weight and probably won't work for very long anyway. When it's 118°F in the shade, stuff gets hot. It's a lot easier and less stressful to simply accept that. With a gallon of diluted gatorade you can hike around the desert for a few hours at least. Let yourself get used to it, and it's really not uncomfortable at all.

Another advantage of gatorade is that you don't need to eat anything. You're not going to starve in one day, you feel less hungry when its hot, and the gatorade provides some sugar. I usually start hiking in the morning and get back mid to late afternoon. During that time, I only take in the diluted gatorade, then eat something when I get back.


Mix the water in with lots of crushed ice - or even just use crushed ice to start with rather than water. I prefer this approach over just freezing the bottle outright because I find it easier to get the water out when I want to.

Other than that, I'd try wrapping cloth and then foil round the bottle (shiny side on the outside) which should help to keep at least some of the heat out. You could also freeze / chill both the cloth and the foil before you wrap them round - that'll provide that extra bit of chill as well.


My idea is to keep your thermos bottle full with ice chips, then when thirsty simply dump some of your ice into a small cup then add your beverage! Save as much as you can by returning the unused ice to the thermos for future use. Of course its best to stick with the same beverage, and or water, so flavors don't get mixed if you use the ice again. I still had ice at the end of an 8 hr. day, in the thermos when I returned home. Temp was in the high eighties, and dry heat!!!


If you only use PET bottle try to put a neoprene sleeve around them. Neoprene is used to insulate the tubes of the so called "hydration systems", that is those bladders with a tube going from the bladder to your mouth when you want to suck water from it. Neoprene works pretty well both in keeping the heat in winter and the opposite as you need. It doesn't do any miracles but it helps.


I keep it in a flask - very cold water so it is basically ice crushed a lot, enough to make it look like water; or ice cubes in a flask under a sleeping bag or in a backpack.

  • I question that this answer will be effective. If the original poster has tried various insulations, devices, and still is not satisifed, then this is unlikely to add much time. Commented Apr 1, 2013 at 1:36

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