Plain lattes aren't bad at all, since they're just coffee and milk. You would have to syn any syrups that you add at 1 syn per pump, but sugar free ones are free.
I'm going to assume you're getting skinny (skim/fat free) ones...
Caffe Latte Skimmed Milk , 1 short - 3½
Caffe Latte Skimmed Milk , 1 tall - 5
Caffe Latte Skimmed Milk , 1 grande - 6½
Caffe Latte Skimmed Milk , 1 venti - 8½
There's a bit of debate whether you can use this as a HEA, I personally do. So either the short as half HEA or grande as full HEA plus ½ syn for either option.
Frappuccinos aren't so good since the base has sugar in them. Again, going to assume you're just getting the plain one, as flavoured would have more syns.
Coffee Frappuccino, No Whip Skimmed Milk , 1 tall - 8
Coffee Frappuccino, No Whip Skimmed Milk , 1 grande - 11
Coffee Frappuccino, No Whip Skimmed Milk , 1 venti - 13½
If you switch to the Light option, the syns almost halve and really aren't that bad! This is what I have, it's delicious.
Coffee Light Frappuccino, No Whip Skimmed Milk , 1 tall - 4
Coffee Light Frappuccino, No Whip Skimmed Milk , 1 grande - 6
Coffee Light Frappuccino, No Whip Skimmed Milk , 1 venti - 7
I wouldn't try to use these as HEA though, as it's difficult to work out how much milk is in them due to the other ingredients.