Have an easy to find link to the app on the restaurant's website, social media, online directory listings and so on.

I might just be impressed enough to go eat there, if I can check it out ahead of time.

Part of your studies should focus on the inclusive design practices that Apple and Google have developed for app developers. Our phones can read QR codes, although doing that is rather finicky, so it's best to be easily discoverable on the app or play store, be concise and simple, and for the love of Steve, please use native controls as much as possible. Other than that, just making the menu page and the overall website accessible for the restaurant would be fine. Use proper HTML markup and heading structure, don't go all bananas with dynamic features, collapsible sections, and weird interactions that are unnecessary to convey basic information, and label *everything!*

Most delivery apps don't do any usability testing and the interfaces feel really messy when trying to navigate menus, ingredients, prices, etc. I can use Grubhub, but it can be a real pain navigating long menus since they didn't create navigable headings through the screen and have a lot of clutter in the way things are presented.

Do not by any means create a segregated or separate experience for screen reader or assistive tech users! This is very bad form and causes issues when the team that originally created the experience moves on and people forget to update both the main site/app along with the "accessible" experience. You Must focus on making fully inclusive design for the app or site so it's usable by everyone. Make sure your app functions with dynamic type and zoom, uses WCAG compliant color contrast, and actually do testing with disabled users rather than assuming that the flow you created makes logical sense. Remember, our experience is linear as we navigate a screen, so there must be a meaningful and logical sequence of headings, copy, controls, and nothing that requires a user to jump around the screen just to get context.

Create an easy to remember custom URL that lists content in text only

If the customer is already interacting with staff and the app is on the App Store or Play Store, the staff could just give the customer the name of the app and they'd be able to find it...assuming the spelling is close enough to how it's pronounced.

If it's not available on either store, then as has been suggested, make it easy to find on the site. That said, being "easy to find" can differ from user to user.

If you are creating an app or accessible menu of some sort, for the love of God label your buttons! There’s nothing worse than going through an app and finding “button“ “button“ “button”, with no way to tell what those buttons are or what they do.