All your characters should have unique personalities, therefore they will all talk slightly differently.
Now this is impossible to do if your characters haven’t got a personality (this is where character profiles become critical).
So make them cocky, flirty, obnoxious or whatever their personality dictates, but let the dialogue speak for itself.
Play around with it for a while, it will come with time. But until you know what your characters are like you can’t convincingly write their dialogue.