There's a brand of bottled water, I forget which now, that says on the bottle not to put any other water into the bottle.![]()
Exception - all foreign water will give you a runny bum, fact. Bottled water or immodium en mass.

I heard one can not re-use plastic bottles with other liquids as the water will eventually react with the plastic and make it "bad" for you, have no idea how right that is.
Does anybody know(got link to facts) whether bottled water has less bacteria or "bad" stuff in it rather than tap water?
Every time I visit my sister in Bristol, I take a big bottle with me. The tap water in Bristol is terrible. I wouldn't even let my toilet drink it.

My link above covers relevant stuff.
I'll carry on buying bottled water and refilling them a couple of times (max). http://greenliving.nationalgeographic.com/reusing-water-bottles-increase-bacterial-content-3019.html I normally buy some water, then take the bottle home and refill it with squash/water for training or matches... but then get rid after that, because we all share water and I cba getting mouth AIDS from some random prole.
I think this is mainly totued due to the leechables effect of re-using bottles over and over, and then its only really based on polycarbonate based bottles which can leech bisphenol over a long period of re-use.
haven't got any imperical data to hand, but I do remember covering this in packaging material science / tech reports when we were researching material types for liquid preparations in the pharma industry
To be honest, I only buy bottled water for the gym and also to force myself to drink more water. If I buy water it means I have to drink it as I spent money on it. Otherwise I when at work I would drink from the water machine or if at home I would filter and boil tap water.So can I. But would I pay for that difference...![]()
Bottled water only here. But then it's only about 50p for a big 5L thing. I tend to stick to beer instead.
Never used to buy it back in the UK, generally reused an old bottle of something else and filled it with tap water if I wante dto take it out for playing football or something.