Vegetarian
On the street food tours, a vegetarian has few safe options. Hungry Osaka Tours rules vegetarians out, and Osaka Food Tours, Inc. does not mention them. Goen Japan adapts to a limited degree. The kushikatsu and okonomiyaki tour has meat-free skewers, but cooks them in a dashi that contains pork, and its listing now names vegetarians among the guests it is not suitable for. The Shinsekai tours page sets out the rules of each.
Classes are easier. The sushi class has a vegetarian menu, the ramen studio near Osaka Castle cooks vegetarian on request, Cooking Sun offers vegetarian or pescatarian versions on request, and the XLSWORLD ramen class makes a vegetarian version if you ask before the day. The soul food class with the supermarket visit welcomes vegetarians if you tell it a day ahead.
Vegan
No full food tour in this comparison offers a vegan route, and the biggest Shinsekai tours rule vegans out by name. Among the classes, the sushi class has a vegan menu, and the ramen studio near Osaka Castle makes a vegan bowl on request. The Kuromon Market walk accepts vegan requests too, sent at least one day ahead, although market stalls are mostly seafood. The soul food class is contradictory: it welcomes vegans in one paragraph and lists them as not suitable in another, so get a written yes first.
Gluten-free
Takoyaki, okonomiyaki and kushikatsu are all coated in or made from wheat batter, and ramen noodles are wheat noodles. Osaka Food Tours, Inc., Hungry Osaka Tours and Goen Japan all say they cannot serve a gluten-free diet, and Cooking Sun has no gluten-free version of its ramen. The soul food class rules out gluten-free too.
Among the classes, the sushi class offers a gluten-free menu, and a class in Higashiosaka teaches ramen and gyoza with gluten-free noodles and wrappers, for no more than 4 guests. The ramen class comparison has the details. The Kuromon walk is unclear: its listing first refuses gluten-free requests, then accepts them a day in advance.
Halal
The sushi class in Shinsaibashi is the only listing on this site with a halal menu. A guest who booked it for that reason writes that her group was seated at a table where other participants drank alcohol, so the menu is halal but the room is shared. Ask for a separate table when you send the request. The sushi class page covers the class in full.
Allergies
The takoyaki tasting walk in Dotonbori says it is not suitable for anyone with a food allergy. The Kuromon Market walk does not guarantee allergy-free food. Goen Japan can take some allergies into account, to a limited degree. For any serious allergy, write to the operator after booking and wait for an answer before the day; the free cancellation on the booking page gives you time to step back.
How far ahead to ask
The sushi class needs three days’ notice for its vegan, vegetarian, gluten-free and halal menus. The Kuromon walk and the soul food class need one day and cannot change anything on the day itself. The XLSWORLD ramen class asks for vegetarian requests before the class. Where a listing says on request without a deadline, send the request at booking.
On the bar crawls, none of this applies in advance: you eat what you or the group order at each bar, so diets depend on the menu in front of you.