If you run an inline filter and get water trapped in it then just upbolt the banjo fittings and blow throw it, hey presto its water free again. Shit is another matter though, best fit a new one.
That tank cleaner sounds dodgy to me also. Even if it breaks the shit down it still has to go some place, that place being into the fuel and eventually through your carbs or injectors. Best bet is to remove the tank and flush it out, maybe that is what its for??