Soft flasks, water bladders, water bottles - the variety of names we have for the things that keep us hydrated! Today, Im sharing the really simple method I have for cleaning and sterilising my flasks. Ive been doing this for a few years, and so far its worked well on all my plastic food utensils that Ive needed to deep clean after outdoor adventures.The only item youll need to buy is sterilising fluid used for infants bottles. It comes in a concentrate, and the most popular name brand that I know is Milton. Im using an off-brand version I found in my local supermarket. MethodRinse and clean your soft flasks. If possible, try turning your flasks inside out and using a clean nail brush to scrub down the insides. This is great if youve used electrolytes or additives to your water. I use my regular dish soap. Rinse well.Check the instructions on your sterilising fluid - for mine, its two caps of fluid to 2L of cold water. Prepare the mixture in a large clean bowl. Take apart your soft flasks / water bladders. These things come apart more than you would think. Its always important to take apart the mouth pieces, as this is where Ive seen the most mould and bacteria build-up. Check on the manufacturers website if youre unsure how to take yours apart. Submerge your flasks in the solution. I like to leave mine overnight, but follow the instructions that come with your sterilising fluid. For more traditional water bottles, I stand them on a stable surface and pour the mixed solution into the bottles, filling to the brim.Once finished soaking, rinse well. View fullsize View fullsize View fullsize This process wont remove long term discolouration, but can remove mould or bacteria discolouration (see in the video below how my discolouration changes). Between washes I will often store my flasks in the freezer to prevent any new bacteria or mould from growing. Gear Care 101 SeriesHow to fit hiking bootsHow to Wash WaterproofsHow to wash sleeping bags & down jacketsHow to patch a waterproof jacketHow to resole hiking boots