Birds of a Feather at Loggerheads Meitantei Conan : Season 1 Episode 903

Conan, Mouri, and Ran witness Nichiuri Sports reporters arguing at a restaurant. One leaves the restaurant and accidentally takes the other's travel mug with him. That night, a body is found on the riverbank. The cause of death is poisoning by cyanide mixed into the coffee in his travel mug.