expression, godan verb (-ru)
false advertising; bait and switch; cry wine and sell vinegar
Idiomatic expression meaning to advertise something good but deliver something inferior; literally 'hang out a sheep's head but sell dog meat'. Used for deceptive marketing or pretense.
あの店は羊頭を掲げて狗肉を売るような商売をしている。
That shop does business like crying wine and selling vinegar.
看板倒れ means something that looks impressive but is disappointing in reality, similar to false advertising, but it is a noun, not a verb phrase.
The idiom is of Chinese origin, from a classical story about deceptive merchants. The literal meaning is 'hang a sheep's head but sell dog meat', used metaphorically for false advertising.