Smarmy

"The smarmy salesman laid on the compliments so thick you’d think you were his favourite customer, all while nudging you toward the priciest option."

"He flashed a smarmy grin and called the manager’s plan “utterly brilliant” after slagging it off in the corridor."

"Her smarmy apology, all slick charm and faux concern, was clearly more about saving face than making amends."