Kmeta won't work in beer because you need a pH below 4.0 for it to produce any decent quantity of SO2. Above that it is ineffective. some wines are up close to 4.0 and you have to add a rather large dose of kmeta for it to produce enough free SO2.
As for a sanitizer, if you add some acid to your mix it will work fine. Be careful of the fumes, it'll smell of sulfur from the SO2. A couple spoonfuls of acid blend or even viniegar, of course you'll have to rinse afterwards. You could probably use phosphoric and not rinse as long as you drain it well. Typically a concnetration of 1% kmeta in acidified water is used as a sanitizer for winemaking. as for contact time, a few seconds is all it'll take to sanitize.
I use starsan, much easier.