A bottle of ice-cold water makes a refreshing drink, especially when you're sweltering under the blazing, hot sun. Stick a bottle of water in the freezer overnight, and taking it out to thaw a few hours before you need it works, but there are a few more methods you can try.
The Slow Method
Wrap frozen bottles in paper towels if you're on the go, and you don't mind a slow thaw. Place the bottles in plastic bags by themselves. The paper towels absorb the condensation as the bottles thaws. If you're at home, place frozen bottles of water in the kitchen sink or in any vessel deep enough to hold them such as a bowl, pot or a pitcher; let the water thaw at room temperature. Wipe down the bottles' exterior once thawed to your satisfaction, and put them in the fridge if you'd like to keep the water chilled.
The Fast Method
Fill a vessel with warm water from the tap and set the frozen bottle of water down in it. As long as the bottle is plastic and the water is not carbonated, the warm water does nothing more than hasten melting of the ice. The microwave might seem like an appealing alternative to thaw a frozen water bottle fast, but frozen water molecules simply don't absorb microwave energy.