(I don't know if it's okay to ask about two different characters in the same question. I doubt it, but someone please let me know.)
We know that Data's systems can be affected on occasion (see "The Naked Now"); also, sufficiently powerful energy creatures can overtake him ("Power Play"). So I'm wondering if a souped-up hypospray could disable his systems. Could something be devised that could mimic the introduction of an alien program (as what occurred in "Contagion"), or render him asunder in some other way?
Admittedly, I'm not an expert on DS9, so possibly this was discussed during the show. But could a changeling be knocked out by a hypospray? Changelings have high resistance, as shown multiple times, so their "immune system" surely works quite well (except against engineered diseases, of course). As biological beings, I don't see why changelings couldn't be put down by a hypospray, though it'd undoubtedly take much research into the matter.