Is there an adjective for "untruthful, especially when pretending to know more than one actually does"?

I originally thought of the word "disingenuous," except that my dictionary gives the definition as "not candid or sincere, typically by pretending that one knows less about something than one really does." I'm looking for a word that's similar in meaning, but with an emphasis on pretending to know something (rather than pretending not to know something).

Example sentence: Citing statistics he made up, the _____ salesman claimed that his weight-loss pills were miracle workers.

Merriam-Webster's Learner's Dictionary defines the word charlatanic (alternative form charlatanical) as

: of or like a charlatan : marked by or given to pretension and quackery

In turn, the same source defines the noun charlatan as

: a person who falsely pretends to know or be something in order to deceive people

I'd be a little hesitant to use charlatanic or charlatanical, since they are very infrequently used; I'd worry that readers might think I had just coined the word. I'd rather work the noun into the sentence, for example,

Citing statistics he made up, the salesman, that charlatan, claimed that his weight-loss pills were miracle workers.

But the adjectives do exist in some dictionaries if an adjective is really what you need.

[...] the bullshitting salesman claimed [...] .

bullshit
[...]
4. (intr) to talk in an exaggerated or foolish manner.
5. (tr) to talk bullshit to (a person).

Usage: Bullshit was formerly considered to be taboo, and it was labelled as such in older editions of Collins English Dictionary. However, it has now become acceptable in speech, although some older or more conservative people may object to its use.
— Collins English Dictionary:

Note: For a less objectionable variation (if you can rework sentence to use a noun), consider bull - actually an older form, rather than a contraction.

I like the word deceitful in this case:

guilty of or involving deceit; deceiving or misleading others. MW

In the above definition, they give this example:

charged the store owner with such deceitful practices as inflating the list prices for items only so he could put them on sale at drastically reduced prices

In your case:

Citing statistics he made up, the deceitful salesman claimed that his weight-loss pills were miracle workers.

He is knowingly passing false information.