(as|) (phony|queer|counterfeit) as a three-dollar bill

not true, real, or genuine

The idiom "phony as a three-dollar bill" likely originated in the United States in the late 19th or early 20th century. During that time, three-dollar bills were not a common denomination in circulation, making them rare and unfamiliar to the general public. Today, it is used to describe someone or something that is fake, fraudulent, or lacks authenticity.

If she doesn't practice more, her acting will appear as queer as a three-dollar bill on stage, and she won't get the lead role.
In the past, some con artists used to sell phony products, convincing buyers they were valuable, but they were as counterfeit as three-dollar bills.
That email claiming you won a lottery is as fake as a two-dollar bill; it's a scam trying to steal your personal information.
The evidence presented by the accused seemed as phony as a three-dollar bill, and the jury quickly dismissed it.
The politician's promises sound as phony as a three-dollar bill, and people are becoming increasingly skeptical of their sincerity.