What kind of scenario do you have in mind?
If you have a pool of water a couple of inches deep, you can do it in stages. First blow air into it to stretch the rubber a bit. Then hold the mouth open and pull it through the water. That gets you a little water. Squeeze it down to the bottom, and keep squeezing to stretch the rubber more and make room at the top. Hold it in the middle with one hand, keeping the pressure on the bottom half, while holding the mouth open with the other, and pull it through the water again. This will collect some more water in the top. Squeeze it down to the bottom. Repeat.
A condom isn't part of my EDC partly because it is too bulky for me, partly because I haven't found a local source of non-lubricated ones, and partly because I don't want to have to explain what it is to any children that I show my kit to. The above seemed to work when I just experimented in the kitchen. I couldn't get as much water as I could from a tap under pressure, but it was better than nothing. I should think the main benefit of carrying a condom is recreational, but that's not to be sniffed at. Anything that makes sure the kit is with you and not left at home when you need it.
If you have something like a slow drip, you probably need to use two condoms. When the first fills up, transfer the water to the second, using the same staged technique.
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Quality is addictive.