That's right - you're in Texas, aren't you? Oh, that heat. It's exactly why I moved. I have one insulated drinkware cup that is my favorite and no one in the house is allowed to use. lol
It's probably not the most green one available on the market - but it's stainless steel and most importantly - all the pieces come apart for proper cleaning. I cannot abide by those crap-design drinkware containers that harbor bugs in places you can't clean on the lid or otherwise. Ick!!
But - if you're gonna drink outta plastic (job site, whatever) - make sure it's BPA-FREE PLASTIC. Check this out:
If you're gonna drink out of a plastic bottle, this company sells the most healthful plastic bottle currently on the market. All others I've researched that are stainless steel don't have a way to clean them properly - they're either tapered at the top (meaning I'm not gonna get to scrub them entirely) or the top to them has little crevaces that gross me right out. The man drinks outta one of these (mobile job, won't spill, etc):