I have never been a fan of buying bottles of water abroad because of the environmental impact, plus sometimes the expense. It is however important to keep yourself hydrated whilst travelling, especially because flying really dehydrates you and also if you are travelling with small children to hot countries you need to keep them topped up with water. A couple of years ago I came across a fantastic solution. Water To Go produce water bottles that use NASA technology to remove 99.9% of all bacteria and viruses from your water. Each filter can filter up to 200 litres of water before it needs to be replaced.
The filter is reactivated by tipping the bottle upside down for a minimum of 15 minutes. I highly recommend them for adventures off the beaten track. If you do a quick search on YouTube, it is easy to find reviewers demonstrating how clever these filters really are. Here you can see a guy who experimented by tipping Coke into the bottle which then filtrates into water! See for yourself Turn Pepsi into water
I purchased a bottle for both of us about a year ago. Now they are an essential part of my kit. You can buy them here Water To Go