Miss Chu's at the Opera Kitchen has a couple of vegan options for when you are at the Opera House and need a quick bite.
The Opera Kitchen has outlets of a few Sydney restaurants, one of which Miss Chu's has two vegan options. This isn't exactly worth a special trip, but it can be very handy if you are going out to the Opera House or drinking at the Opera Bar next door (which happens more often than you would think). The Opera Kitchen also has serves vegetarian (thus vegan) chips from Charlie and Co.
Vegan status: three options, warm vermicelli mushroom salad, tofu vietnamese rice paper rolls and hot chips.
Price range: between $10 and $18.
Sydney Opera House, Lower Concourse, Circular Quay (Bennelong Point)