We’ve had a few discussions in the IM=X Pilates studio about water bottles, both plastic and metal. I’ve done some digging (mostly at idealbite.com) and here are concise answers to some of your plastics questions:

What is the best plastic bottle to reuse?  #2 plastic- HDPE plastic, soft and opaque. Think “The ants go marching two by two, the little one stopped to tie his shoe…”, 2001: A Space Odyssey, Two Pina Coladas- you get the idea.

What are better choices? Glass and stainless steel.  (Aluminum needs a coating over it.) Sigg bottles, or leftover glass juice bottles are in this category.

What is unsafe? Copied directly from [1] Ideal Bite:

Note: [2] Nalgene does now carry an Everyday brand bottle made without bisphenol-A.

What about recycling? Here is a list, again from [3] Ideal Bite, of plastic numbers and recycling:

Usually recyclable:
1. PET - 2-liter and mouthwash bottles, boil-in-bag pouches.
2. HDPE - milk jugs, trash bags, detergent bottles, some yogurt cups.
Sometimes recyclable:
4. LDPE - grocery bags, produce bags, food wrap.

5. PP - diapers, straws, yogurt containers.

6. PS - CD cases, egg cartons, Styrofoam.
Not so much…
3. PVC - cooking-oil bottles, meat packaging, office binders.

7. Other - other types of plastic, plus things made from more than one type of plastic (see below).
Bioplastics (7, and marked as either compostable or biodegradable):
7. Compostable Plastic - is nontoxic and breaks down as fast as paper in compost.
7. Biodegradable Plastic - may contain toxins, so you have to send it to a special composting facility (enter compost and your zip at Earth911, see below).
Commonly questioned items:
Container Caps - typically different plastics than the container; take ‘em off, check the # inside, and either recycle or throw them away.
Grocery Bags - reuse them first! You usually can’t recycle them curbside, but some supermarkets have bins in-store.
Earth911 - find out if you can recycle specific items in your area.

 So, here’s a summary: we like glass or stainless steel for sipping during your brief pilates breaks, #2 plastic is also ok, and you can recycle most stuff.