Bottled water is never a good environmental choice, but it's an especially ridiculous one for a summer outing: It's heavy, requires a recycling bin, and is expensive. Instead, take along the TapGuard self-filtering water bottle insert for better-tasting aqua no matter where you are; while it's not going to make unclean water safe, it will reduce chlorine and improve the taste of regular tap water.
The widemouth filter fits into the bottle you already have, and replaceable cartridges clean up to 100 liters of water each. (TapGuard, $16)
Photo via TreeHugger