keeps 'em clean
I've had the SIGG bottles for a long time, and a soapy water rinse just doesn't get rid of the metallic taste. These work great, I use them on my thermos also. They are fizzy tablets, maybe just Alka-Seltzer would work next time.

Too expensive for what it is
Like a previous reviewer, I use denture tablets for my Sigg and Camelbak stuff. This is an expensive alternative.

Beware - Just Expensive Efferdent Tablets
I was disappointed to open the box and discover these Sigg cleaning tablets are basically repackaged Efferdent tablets with a much higher price tag. I use Efferdent tablets to clean flower vases quite effectively and, after I use up the box of Sigg tablets, I will switch to the way less expensive Efferdent tablets.

Cool I guess.
They are cleaning tablets. Kinda sucks that you need to buy special tablets to clean the bottle, but they are cool I guess.

Not so much rinsing!
I love my Sigg bottle--it is nice and lightweight and, so far as we know, does not have potential to leach toxins, nor does it impart a metallic taste. The downside is that it isn't dishwasherable.

Using dishwashing liquid to clean my bottle means a whole lot of rinsing to get even the tiniest drop out. These tablets also require rinsing, but once seems to be enough. They take 30 minutes to work, and aren't cheap, but they sure are easy.