If they are where there is adequate water available I think I would change out one to the Nalgene bottles for a filter type bottle, that way they just need to fill that bottle and squirt it into the Nalgene for filtered water.And I might also add a small alcohol stove or a Esbit stove. The alcohol stove would be better if used inside a stranded car.

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Some people try to turn back their odometers.
Not me, I want people to know "why" I look this way
I've traveled a long way and some of the roads weren't paved