On a television drama a man spiked a girl’s drink. She was suspicious and so dipped her finger into it. It was a dark scene so I couldn’t really see what happened but her nail polish on that finger either changed colour or dissolved. Is that a way to test for a spiked drink and, if so, how does it work?
It's not clear that such a product exists. This more recent link suggests that the nail polish idea was proposed, but ultimately abandoned. A shame, because it really would have been a fine idea, and perhaps one day it'll be revisited.