The Wetherspoon app currently does not allow customers to order vodka mixed with Irn Bru directly as a preset drink option. The app provides a straightforward method to order both food and drinks to your table, including a wide range of vodkas and some soft drinks, but specific mixed drinks such as "vodka with Irn Bru" are often not available as a single, selectable item137. While Wetherspoons does have an "expansive selection" of vodkas and offers soft drinks, Irn Bru is not listed as a default mixer on their main drinks menus57.

Possible solutions:
- Order separately: You can order a vodka (such as Smirnoff or Absolut, both widely available at Wetherspoons) and a bottle or can of Irn Bru as separate items using the app, then mix them yourself at the table (if Irn Bru is stocked at your location)257.
- Ask staff: If you cannot find Irn Bru as a soft drink option on the app, you may need to approach the bar staff in person to request it, as some Wetherspoon pubs do carry bottled Irn Bru, particularly in Scotland or during special events, but its availability is not guaranteed at every location2.
- Comment/request feature: The current Wetherspoon app does not appear to have a "notes" or "special requests" function for drinks orders, a limitation noted in user reviews3. This means you cannot simply request "vodka and Irn Bru" in the app’s comment section.

In summary: The inability to order vodka with Irn Bru as a single drink through the Wetherspoon app is due to the limitations in how the app processes cocktail or custom mix requests, and possibly due to inconsistent Irn Bru availability137. Ordering both components separately and mixing them at your table is the most reliable workaround, provided Irn Bru is available at your chosen pub.