For those wondering about the soapy water, it effectively suffocates the hornets because soap allows the water to penetrate and clog the spiracles which prevents them from breathing.
Soapy water is actually a powerful insecticide against many arthropods:
It does seem to work on insects resilient to other poisons for sure.
We used a mix of vinegar, soap, and water in a spray bottle to rid our patio of earwigs this year and it seemed to work incredibly well. The insecticides we were spraying them with before trying the soap did absolutely nothing but cost $7 a can.
Soapy water is actually a powerful insecticide against many arthropods:
https://extension.colostate.edu/topic-areas/insects/insect-c...