Katherine Hepburn only drank water throughout The African Queen production as a protest of Humphrey Bogart’s alcoholism. However, most of the cast and crew became sick from the water and only Bogart was unaffected because he only drank whiskey.

"The cast and crew endured sickness, and spartan living conditions during their time on location. In one scene, Hepburn was playing an organ but had a bucket nearby because she was often sick between takes. Bogart later bragged that he was the only one to escape illness, which he credited to not drinking any water on location, but instead fortifying himself from the large supply of Gordon's gin he had brought along with him." ^[11][12]

[Wikipedia]