These foreign travel tips are from my own experience.
While you go on foreign travel, you should always drink bottled water to be on safer side. The simple reason is water contains different sets of microbes and mineral deposits that your body might not be used to. Even if the water is normal filtered but tap water, you should better avoid it.
The local residents are used to the water quality whether it’s pure or impure, but foreign travelers most of the times fall prey due to change in water. Rather than investigating the reason later, it’s important to take the precaution.
Don’t buy bottled water at hotels or airports if it’s not necessary and if you are buying it for extra storage. After reaching to your destination, buy it from the local super market, and you would get 2 bottles in the prize of 1 bottle almost.
When in the foreign country, check with someone about the best brand in bottled water in that particular country. I have experience of bottled water not being good quality if the brand is not known.
Make sure that the bottled water is completely sealed and the seal is not tampered with at all.
Use bottled water for anything you would do that gets the water in your mouth. For ex: Rinsing the tooth brush shall be done by bottled water too.
Do not use Ice in hotels in soft drinks or liquor. Rather order for a chilled drink without ice. Most of the hotels, would pour the soft drink in a glass and add couple of ice cubes. If that happens, change the soft drink right in front of you.
Be safe, and drink bottled water in your foreign tours.