Have you considered selling Huel on flights?
Especially Wizzair or Ryanair would be great. If I can pick only one, please Wizzair.
They already sell food and drinks, but the sandwiches are really bad. I would happily pay the price for a sandwich and get a Huel RTD instead, maybe even at a premium to a sandwich.
Or even the Hot & Savory would be a good alternative to their Instant noodles.
Or if all else fails maybe Huel in airport vending machines after security?