An experiment I did was wildly successful.
I'd learned years ago that insects don't drown in water because their spiracles (the body pores they breathe through) have been calibrated by evolution in concert with the surface tension of water.
Given that soap REDUCES that tension (making water 'wetter'), I wondered if SOAPY water might drown them.
It does. Very well. I filled a small spray bottle with water with a little dish soap. One day of spraying seems to have killed all stink bugs I found.