Yep. He sure is. That's Juan Manuel Marquez, who apparently ends his workouts by pissing into a cup and the chug-a-lugging the whole thing. I think HBO may be taking this "24/7" thing too far.
The documentary series is following Marquez as he prepares for his showdown with Floyd Mayweather on September 19 and thanks to their intrusive, omnipresent style, viewers are finally clued into this utterly disgusting training technique. Marquez explains that a lot of vitamins in your body get expelled through urine, which is sorta true, so he figures the best way to get them back is by drinking your own piss.
Has he considered—and I'm just spit-balling here—maybe, I don't know ... taking more vitamins? (Yes, I have considered the possibility that Marquez is simply fucking with all of us [and Mayweather] but the man does get punched in the head for a living.)