I did exactly that, at SYD, after the screener refused to allow me to drink the water, or to empty the bottle into the confiscation bin. I had only about 2 ounces of water in the bottle. FWIW, this was a flight AKL>SYD>DXB, and I had already been screened at AKL and would be getting back on the same plane in less than an hour. We had to get off the plane and go directly through re-screening, without passing any bathrooms on the way, where I could have emptied the bottle.

ME: I'll drink the water.
SCREENER; Oh no, Madam, you can't do that.
ME: I want to keep the bottle. Can I empty it into the bin?
SCREENER: Oh no, Madam, you can't do that.
ME: Do you have any plants I can empty it into? (Yes, they did, very close to the screening point.)
SCREENER: Oh no, Madam, you can't do that.

So, I emptied the water onto the floor. Much shouting and confusion, calling for a supervisor etc. I thought I wasn't going to fly any further that day but, eventually, they let me through, after giving me a long lecture about the danger of someone possibly slipping on the water.

Memo to self: Next time, drink the d*** water on the plane, or drink it at the check point, even if told I am not allowed to do so.