Since we only review FDA-approved purifiers, our testers focus not on effectiveness, but on convenience, flavor, and portability. In those categories, the Aquatabs get a solid thumbs-up.
The sodium dichloroisocyanurate pills, billed to neutralize giardia, viruses, and bacteria, are easy to use, taste-free, and come in watertight foil wrapping. Pop one out and drop it in a 1-liter bottle of water; wait 30 minutes, then slurp away. $13 for 30 tablets; 0.14 oz.; msrgear.com