Drink water from the tap,instead of buying single-use bottled water, which requires much more energy to produce, store and transport. Barely 20% of those plastic bottles end up getting recycled, and most are made out of petroleum.Use filters if you are concerned about your local water supply.
Buy a reusable bottle to take with you on the go, so you can always refill it from a tap and avoid buying bottled water. Stainless steel is a good choice, because you don´t have to worry about the potentially toxic chemicals that can leach out of many plastics over time.