fair-weather
mod. temporary; insincere. (From fair-weather sailor.)I need something more than a fair-weather friend to help me through all this.Well, I see you are just a fair-weather golfer like me.
jive
mod. deceptive; insincere.Don't give me all those jive excuses.I listened to her little jive speech and then fired her.
smarmy
mod. insincere and obsequious.He's obnoxious but brazen rather than smarmy.He's a smarmy creep.The guy is so smarmy, I can't stand him.