No Heineken

A bartender was tending his bar as bartenders are want to do when a scowling man shuffled to the bar, slammed down a ten dollar bill, and said, "Barkeep, I want a beer. Any beer will do. Surprise me. Just make sure it's not a Heineken." The barkeep thought it a weird request, but he shrugged, poured the man a Bud, and watched him drink it and leave.
The next day, the same guy came back, still scowling, and said, "Barkeep, a beer. Anything at all, so long as it isn't a Heineken." The barkeep perked an eyebrow at seeing the strange request again, but he poured the man a Guinness, and the man drank it, paid, and left.
The very next day, the same man came back. He was about to speak when the barkeep interrupted him. "Yeah, yeah, buddy, I know, no Heineken," he said. "I'll get you your beer, but if you don't mind me asking, why the hate for Heineken? It's a fine beer."
The man pinched his brow, sighed, and said, "Well, the thing is, about a week ago I was at the bar and had one too many Heinekens, and when I got home I blew chunks."
The barkeep said, "Well, that's gonna happen if you drink too much on any beer, pal."
"No, you don't understand," spoke the man. "Chunks is my dog."