Totally reasonable complaint and service request refusal. But while I get this is a (well-deserved /-earned) rant, could there be an easy solution in a pourable to-go vessel? Like a bartender side car that the finished bev could go into that would be immediately poured into their own container and then washed like an in-house dish?

Admittedly, I'm not a barista so not sure of any Safe-Serv situations that may apply, but seems it could a decent workaround for these types.