Well, this is clearly NOT Burger King, and you can not have it your way.
For some reason asking for extra coffee sweetener in your coffee means "please don't put any cream, sugar, or sweetener in my coffee".
Same goes for light sweetener. "Please put as much sweetener as you can in my coffee)
Staff is rude and slow. Business inside is not as clean as one would hope... But it's McDonald's, so I guess expectations shouldn't be high there.
"Fast food drive thru" is ANYTHING but fast... So if you're planning on grabbing a snack or something on the way to work, give yourself and extra 30 minutes.