You are advised to only drink bottled water out there, it is true that various brand of water have different mineral content however that is true of all brands in all countries.
Take a look at this guide and compare the various values in water content from different countries and brands, note even the well known brands have big variations
http://www.mineralwaters.org/index.php?func=country the higher the Total Dissolved Solids (TDS) the higher the mineral content.
Here are some examples of well know brands and their TDS, you would not even think twice about not drinking them
Perrier, France TDS = 475
San Pellegrino, Italy TDS = 1109
Highland Spring, UK = 158
Stretton Hills, UK = 226
You will be fine drinking bottled water, if you are sweating and losing body fluid it is also a good idea to drink those sports drinks such as Lucozade Sport, Gatorade, Powerade etc as water alone contains no carbohydrate or electrolytes, this will explain -
http://www.brianmac.co.uk/drinks.htm
Graham