I dunno if this is intended or not, but part of the reason this is funny to me is that pineapples contain an enzyme which digests human flesh. That's why your mouth stings a bit while you're eating them. They eat you back.
I thought the blood pack was an ID meaning the pineapple was a blood donor, so I thought the joke was that the man was having an ethical conundrum about whether to eat the delicious pineapple or to let him live cause hes a good citizen who donates blood.
My mind is in weird places tonight.