I'll add that many people suffer from unnecessary, seemingly "chronic" headaches. When my husband comes home with a headache the first thing I ask him is if he's had enough water. Typically the response is no and more typically the headache goes away after filling up his H20 tanks. I highly recommend reading this book for more information on the healing benefits of water.
Water can be extrodinarily warming or cooling so on hot days, try a glass of cool water for some heat relief. On cool days, vice versa is true. However, be careful not to take in to much water just prior to or soon after eating a meal as it can dilute digestive juices, thus compromising healthy digestion. Really cold water can have the same effect, so generally room temperature water is best.
As for water bottles, I am a huge HUGE proponent of glass for all things that touch food or water. Recent studies are showing that even if plastic is free of BPA, it still can leach harmful substances into your water and food. Lifefactory created a glass water bottle that I love. Check it out here. If you are interested in reading more about plastic and the hazards of, look here.
The moral of the story is drink more [pure] water!