You ask the waiter if they have a special vegan or vegetarian menu. The waiter responds by saying we do not have an official vegan or vegetarian menu, but we could possibly work out an arrangement.
The waiter tells you which products could have substitutions. Vegetarian/vegan soups and dressings are available, but are an up-charge. Since you care about your diet you shrug your shoulders and deal with the up-charge.