IMHO condoms in survival kits, for other than their original intended use, are an anachronism. The idea of carrying water in them goes back to the 40s when plastics were new and there really wasn't much available that was light, compact and collapsible that you could use.

Lacking anything better soldiers were told to use condoms. Which are pretty miserable as water carriers. A latex condom only carries a small amount of water. Less if you try to tie or roll the top. If you tie the top the odds are that you won't get the knot out without destroying the condom. Rolled they are always in danger of leaking. A clip of some sort helps.

Even if everything goes well the latex is sensitive to sunlight and petroleum products. A little oil or grease, or a tropical sun and a day or so is all you can count on. And that assumes you don't drop your water supply, and sharp rocks or thorns don't puncture it. Anyone who doubts this needs to fill a couple of condoms and then try going for a hike using them as your canteen. With near infinite care, the condoms kept in a sock to protect from UV, oils and sharp edges and a clothespin used for closure I got mine to last for two days with one having a pinhole leak near the top. And this was with minimal traveling and movement.

I have been told the large size and extra-thick polyurethane condoms are much better. I may have to try them. They may be more adapted for water storage but, ironically, lass adapted for sex.

My choice has been Platypus bottles. These are tough collapsible tri-laminate plastic bottles. They roll up and remain compact until needed. I have found two of the half-liter bottles fit nicely in my PSK and they are much more practical than messing with condoms or tiny milk bags.

I try to have my water storage divided in at least two parts for redundancy. It also allows you to be drinking from one while waiting for the chemicals to purify water in the other. The larger one-liter version are nice and work well with most available water treatment tablets at the usual dose of one tablet per liter/quart. The larger two-liter bottles are handy around camp and they have a line bladders for hands-free hydration and 2L to 6L carriers for hauling larger supplies.

They are not entirely bulletproof, they can be punctured, but with care they stand up to a lot of abuse. If your careless thorns will poke tiny holes. The same company produced a form of glorified tape that will permanently seal minor leaks in the field.