Review (5/5): Wipe Away!
These will get the job done. It requires you to have water (obviously) but usually if you are camping or deserted on an island, you should be able to find some water. Let it soak for a minute or so and then you have to slowly pull it apart a bit. It ends up feeling similar to a wet wipe type thing. They are small enough to where you can pack them into your backpack, suitcase, shoes, or whatever you need.
In all fairness, I got these as a gag gift and haven't personally used them, but they do feel like they'd be effective. So I'd due to how small and cheap they are, this should be a camping/desertion essential!