I do NOT know if this is factual, but my husband and I were talking about this local area man and trying to figure out what happened to him.
Hubby, who watches 20/20 and that genre of expose' news stories, said that he'd watched a special about the open liquor bottles some of the Mexican and US to the Caribbean resorts pour from at their bar areas.
He said that they will keep the premium bottles spiked to pour, but will refill them with an entirely different product. Like " Bacardi Rum" might actually be a dangerous methanol/ alcohol blend that's $2.00/ multiple gallons.
He said that people who drank too much, or weren't usually drinkers thus were more likely to accept an " off" tasting drink were experiencing things such as blindness, brain damage, pulmonary edema ( life threatening fluid in the lungs), all the symptoms listed under " Methanol poisoning". Methanol is NOT safe for ingestion and has been implicated recently in many side effects from cheap hand sanitizer. ( Always wash hands with soap and water to avoid this accidentally).
Other contaminants were mentioned, but Methanol was the one that was truly the killer ingredient.
Another thing was swelling of the brain from contaminants, either intentional, negligent or purposeful. Swelling of the brain causes confusion and disorientation in its earliest stages.
I don't know firsthand how prevalent this is but if the drinks are free, they are probably not using the premium liquor listed on the label every time, or maybe most times, IMO. Profit margin and all that.