As long as you buy the light and unsweetened version, alpro soya milk is 0.1g carb per 100ml - so 1 carb per litre.
It's funny I never used to like it either, but that was when I was having the normal, sweetened version. The unsweetened light version is much nicer, or maybe my taste Ida have changed - I don't drink much of it neat but like it a lot in tea and recipes - doesn't seem to curdle either.