Alright, after consulting with a few of my professors (all lawyers, though mostly in international law), they said that your friend has maybe one toe to stand on. Unless the image was copywritten BEFORE it was placed on the internet, you're pretty much toast.

He might want to think about asking Pepsi for simply a mention or the like.

Make sure not to say or do anything offensive, Pepsi is horrible about countersuits.

I'll do some poking around in the library here, I've got a few books to look at, but things don't look very good.