Very Mad!

Send it to me - I like my soda flat! :o)

Return it to the place of purchase. They should reimburse you.
You did not include the lot number from these cans either so how is
anyone to figure out how long you had these.

You could also make a phone call to them about this and like Olie
says, they may send you something too.

Pepsi contacts them. I know you are optimistic that they will but I'm
the skeptical one.

seems to be that he should have included the package information in
the body of his letter so Pepsi would be able to easily identify the
source and help them determine the particulars of the case.

Presumably, and according to the other commenters who suggest he
should have put that info in his letter, once Pepsi has that info,
they can and should reimburse him. Which means they would have to
contact him.

If they're going to contact him anyways, why can't they get the
package info at that point?

And if they're NOT going to contact him, then what difference does it
make if he includes the package info or not?