If any drink with juice does trigger the reactive straws the bartenders can learn about which drinks do that and then only serve those drinks without any juice/other material that triggers false positives with the special straws.
Hopefully, you can find special straws that look the same as the normal straws you give out so that an attacker wouldn’t know whether the drink of a target has a normal or a special straw in it.
Then write on the drink menu that some false positives are expected and patrons who have their straw change color should simply come with the drink to the bar to get it exchanged for a new drink as safety precaution.
Whenever that happens you can do more expensive testing and if it triggers correctly investigate the video tapes.
If any drink with juice does trigger the reactive straws the bartenders can learn about which drinks do that and then only serve those drinks without any juice/other material that triggers false positives with the special straws.
Hopefully, you can find special straws that look the same as the normal straws you give out so that an attacker wouldn’t know whether the drink of a target has a normal or a special straw in it.
Then write on the drink menu that some false positives are expected and patrons who have their straw change color should simply come with the drink to the bar to get it exchanged for a new drink as safety precaution.
Whenever that happens you can do more expensive testing and if it triggers correctly investigate the video tapes.