For those of you who have joined the challenge (which is almost over by the way), here is what Grist's Umbra had to say about some re-useable water bottles...
Manufacturing plastic is resource-intensive and yields various nasty emissions that contribute to global warming and degradation of water quality. It's made from non-renewable resources, and for all intents and purposes, it never biodegrades (although some specialized variations have been made specifically to do so). Yes, we'll run out of oil eventually, but we'll always have our plastic garbage. Add to this the growing suspicion that plastic use may lead to serious health problems.
I would generally advise against using plastics in food- and beverage-related applications.
The contradictions you see in the press are a mix of confusion about types of plastic, misinformation, and bona fide scientific uncertainty about the effects of an entirely new group of substances. Snopes.com addresses purported links between PET (#1) and DEHA (di-2-ethylhexyl-adipate), a potential carcinogen, links which are apparently based on a study later shown to be bogus. PET evidently does not contain DEHA, and the carcinogenic properties of DEHA itself are hotly debated.
Nalgene bottles, made of polycarbonate (#7) or "Lexan," are more closely linked to bad stuff, specifically an ingredient called bisphenol-A (BPA). BPA is an endocrine disruptor that mimics estrogen and has been linked to aneuploidy, adipogenesis, and other scary problems with funny names. Drinking water or eating food containing leached BPA may cause chromosomal disruption, miscarriages, birth defects, or obesity. Eek!
#1 bottles are okay; #7 bottles are no good.
Moving on, I would categorically avoid PVC (#3), aka vinyl, for food containers or anything else. It truly is an evil plastic, practically a fount of dioxin. PVC containers and PVC film can contain oft-debated ickies DEHP and DEHA, and some contain softening phthalates linked to liver and kidney damage and testicular problems. Also, polystyrene (#6) is yucky -- it's made of styrene, and you don't want any styrene in your precious bod, trust me.
That leaves us with the winners of this dubious contest: HDPE, LDPE, polypropylene, and limited use of PET.
Glass vessels will work in low-impact situations, and I've seen metal canteens that may suit your needs. It's the biking and hiking and bungee jumping that pose a problem.
From the Brooklyn Green Team: Try Sigg water bottles and Swellz