A totally ripped Gyllenhaal was shooting scenes for the forthcoming reimagining of the 1989 film Road House, playing an ex-UFC fighter. He staged a weigh-in with former UFC fighter Jay Hieron, who plays his opponent in the film. After weighing in, he faced off with Hieron and slapped him, all part of the script.
The original Road House is mostly forgettable but kind of trashy (in a good way), and I don’t remember any scene in the movie featuring a weigh-in like this or a boxing match? More footage of Gyllenhaal and Jay Heiron: