Smarmy (adjective)

1. Insincere or excessively flattering in manner or speech.
2. Ingratiating and superficially charming.

Origin:

From smarm + -y.

Examples:

1. The smarmy salesman tried to charm the customer into buying the product.
2. The smarmy polititian's speech was filled with empty promises.
3. The smarmy actor's compliments seemed insincere.
4. The smarmy waiter was always trying to upsell the customers.
5. The smarmy host's insincere flattery made the guests uncomfortable.