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.

Not necessary but nice to have
I think it's great to have a pack around but probably not something you have to replenish frequently if you only use it for a full disinfection on the bottle every once in a while. I think investing in a sigg bottle brush is just as good for cleaning the bottle.
It's basically dropping a tab into the bottle, fill the bottle up to the neck with water, and let it soak for a few minutes, then you are done!