A great example is Duracell.
They parked a truck filled with batteries and equipped with charging stations in one of the hardest hit areas of lower Manhattan and helped people.
They weren't selling batteries. They didn't charge a fee when you charged your phone. They donated these things knowing that they were creating a brand impression more powerful than any :30 second television commercial or promoted tweet could ever achieve.
It's the same reason people feel good about Chevrolet for donating 50 trucks to the American Red Cross in the wake of the storm or Tide when they bring their laundry truck to town after a natural disaster: they're actually helping, doing good, solving a real problem, providing something that people actually need. And yes, they're also making sure those who have used and appreciated these services know who provided them.
None of the retailers did that. They just tried to take advantage of the storm in a brazen attempt to sell stuff.
So if you feel compelled to make news by attaching your brand to a disaster like Sandy, find a genuine way to use your products and brand to help first.
There will be plenty of time to sell later.