ヴィーガン and ビーガン are the same word written two ways. On a pack or a menu it's the best sign you'll find, but not a guarantee. The word isn't legally defined on Japanese food labels. Some products carry a vegan certification logo, most don't. A dish can be called ヴィーガン and still be fried in the same oil as fish, or sweetened with honey. In Tokyo more and more places know the word. Asking about dashi and honey covers the usual blind spots.