Travelers Against Plastic is a non-profit organization encouraging travelers to reduce and eliminate their use of plastic water bottles. Having lived on False Bay, a community on the coastline of South Africa, I can't tell you how discouraging it is to see plastic waste wash ashore every day. Not to mention, the plastic bottle creation process is taxing our environment, too. You can join me with a pledge to reduce your use of plastic water bottles on the Travelers Against Plastic website.
How can you stay hydrated while traveling and also avoid purchasing plastics? The first and easiset option is to carry a reusable water bottle with you. Kleen Kanteen's wide mouth bottles are water filter compatible. Keep your bottle in the refrigerator overnight and a cool, refreshing drink awaits you the next morning.
The second option is water purification. Tablets are often the cheapest method to rid local tap water of nasty bacteria. Personally, I don't like the taste of the water after using tablets. Other methods of water purification include the SteriPEN, which uses UV light to purify quickly (bonus: they have USB rechargeable versions).
If the tap water is not safe to drink where you're traveling to and you can't purify it using the methods above, when you arrive at your destination, buy one giant bottle of water (1 to 3 gallons) as supply. You can refill your smaller reusable bottle from the big bottle each morning. It's so easy, you'll never go back to buying plastic bottles while traveling again.