One thing to watch for is that the location of the bottle in the sun can be a concern. You can actually have a prism effect that can catch the grass behind it on fire. At least one forest fire has been attributed to a prism effect from a discarded water bottle. Highly unlikely to happen, true, but worth keeping in mind.
Gunco Member #10
The "original" Boltcutter Rivet Squeezers:
Project Pink - the Pink and Blue AK-74:
I'm not sure why anyone would prefer taking the time to wait on UV rather than just boiling the water for 5 minutes. Hate to say it, but my survival equipment includes a metal Sierra Cup, at a minimum.
There are times that you do not have fire, or do not want to risk exposure with a fire. SODIS works with or without fire.