I have done it twice! The best one was when my mate was not drinking because he had damaged his stomach lining by drinking. We were in the pub and he ordered a water, I was mad drunk on pints and had noticed how clear my pee was. So I got a glass, wheeked off to the toilets and came out and grabbed some ice and plopped it in my relatively clear pee. When I returned he has a sip and said, what the funk, is this piss.

I laughed and laughed, of course I had to run away because he wanted to throw it over me and/or punch me.

Great times, the second time was more spiteful.. 😃