I remember those from either Hurricane Frederic in 1979 or Elena in 1985. The ones they gave out back then were carbonated water, and tasted horrible, but at least they were clean water. Where I lived, we had (and still do have) well water, not city water, so since our power was out our pump wasn't working. No pump = no water. Anything was better than nothing at that point.
They did this when the flood of '98 hit the area I once lived in Caldwell,OH area..... they gave us white cans with the AB logo on them that were filled with filtered water. pretty cool. I believe my mom still has one as a collectors item!