i just looked this up in my Food Additives book and this is what is says:
"the same as sodium bisulfite. the additive is unsafe or very poorly tested. destroys vitamin B1. small amounts may cause asthma, anaphylactic shock; dangerous for asthma and allergy sufferers; has caused death; banned on fresh fruits and vegetables except potatoes."
i know that this doesn't really tell you if it's vegan or not, but maybe it will help decide if you even want to drink it.
ah, what the FDA allows to be put in our food...