Most cafes offer some vegan options, for instance that cyclist favourite beans on toast. I don't think any vegan audaxers are asking that a commercial control should serve solely vegan food, just that some vegan food be available. The vegan mountain run someone linked to is clearly a different thing entirely, it doesn't use commercial controls (from what I could gather) and is organized explicitly as a showcase of vegan athleticism. I don't know if that would work as an audax as AUK might think it unduly restrictive for an organizer to require that entrants only eat vegan food during the event, though I don't suppose there's actually a rule relevant to it. That's not the same as the organizer only offering vegan food, that seems quite reasonable.