I did not personally see him peeing in the bottle, but have had to clean them up after the fact. Actors are typically given water bottles and are essentially the only ones who would have them handy on set. Oftentimes, they’ll forget to grab them on their way out. Typically not full of piss. I’ve worked with plenty of other actors that do NOT leave behind piss bottles. It’s disgusting and unheard of anywhere else.

There are nearly always bathrooms nearby for the crew, whether portable or otherwise, so there would be no need for them to piss in a bottle.

I also have friends who have worked on other projects with Dwayne Johnson and can corroborate the piss bottles.