You can use it as a HexA if you have it with skimmed because a tall is just over 350ml, I'm not quite sure about the syns because I always use it as a HexA.
I really don't think they are sugar free...in my old SW Directory(2005) it says a Mocha Syrup shot is 4.5 on green and 5 on red...so the caramel etc are probably even more! :-(