Use 95% pure ethanol, sold in liquor stores as "rectified spirits".
Just a small amount is all you need.
Slosh it around the container and it will pick up every last speck of water and evaporate it, leaving the interior of the container bone dry.
Caveats: (1) Do not use 70% alchohol, that will not work (2) Do not use "denatured" alcohol under any circumstances.
It contains a solid chemical called denatonium which tastes terrible and which you do not want to be in your container.
lifehacks.stackexchange.com/users/5292/Tyler Durden
My solution for storing multiple Camelbak bladders for long periods of time without any mold or mildew inside is to fill them with water and then make sure ALL of the air is bled out before storing.
Mold and mildew need air to grow so
if the interior has no air or bubbles of any kind, presto!
Nothing will grow!
Just fill the bladder with water then flip it so the hose is at the upper end of the bladder and jiggle until all the air is at the base of the hose.
I then use the mouth piece to suck out all the air.
If you're going to store it for a really long time, do it again until there is absolutely no air inside.
This absolutely works perfectly.
I've been using this method for years.
lifehacks.stackexchange.com/users/11642/PJNoes
Since there are narrow spaces at edges, it may not be practical to completely dry it.
However, if you rinse with dilute chlorine bleach or water with a treatment tablet, and then pour and squeeze out as much as possible, there should be enough residual chlorine to prevent algae or fungus growth.
lifehacks.stackexchange.com/users/2012/DrMoishe Pippik
What i do is flip it upside
down(where the water hole is facing downward) and stick a couple napkins inside overnight
and it usually does the job.
lifehacks.stackexchange.com/users/9608/oscarmk4
I dried mine out all I could with kitchen roll then filled it with some more and left it opening-down in the airing cupboard for a day or so.
Maybe not the best way
but it seemed to work for me
lifehacks.stackexchange.com/users/9849/Airglow
I would follow the instructions here, under Product care.
http://shop.camelbak.com/reservoir-dryer/d/1125_c_326_cl_924 Also, buy one of those things.
I don't actually own or use a camelback.
I just used the internet.
lifehacks.stackexchange.com/users/9494/user70848
You can insert the tubing inside the container such that opposing walls don't touch and leave it open for a day or two till all water is evaporated.
lifehacks.stackexchange.com/users/9855/helge
The  Camelbak  is an useful piece of equipment for long outdoor hikes, cycling trips, and camping trips. It stores water in a pouch, with a tube to drink out of.    But that's my problem:   After I'm done using it, how can I dry out the tube and pouch quickly and well, so that it doesn't mold (or get gross!)?
How to quickly dry out a Camelbak?
lifehacks.stackexchange.com
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lifehacks.stackexchange.com/questions/9413
lifehacks.stackexchange.com/users/9561/Numeri says Reinstate Monica
There are number of different ways to dry out a Camelbak. Once method involves rinsing with 95% pure ethanol. Another method is to rinse with dilute chlorine bleach or water with a treatment tablet and then squeeze out as much as possible. Finally, instead of drying, you could simply store it full of water, having made sure that all the air has been bled out before storage. The options are to rinse with 95% pure ethanol, fill with water and remove all air, rinse with chlorine and squeeze out.
Rinse with a small amount of 95% pure ethanol. Fill with water and make sure all air has been removed before storing. Rinse with chlorine bleach and then squeeze out.