In Vietnam, if you couldn't get PBR, there was the native brand Ba Mu'o'i Ba (Thirty-Three). It is said that to keep it from going bad in a tropical country with few refrigerators, formaldehyde was used as a preservative. The brew was even celebrated in song: Ba Mu'o'i Ba by Barry Sadler (1966).
Today, this beer is available in the US in some places and it actually tastes pretty good.
"We put in just a touch of formaldehyde for flavor."
Interesting. Thanks.