The sandwich is served on toasted sourdough with rocket, cheese and pickles.
Its barbecue sauce is made from pulled jackfruit and mushrooms - roasted in Irn Bru.
The sandwich also comes with side-salad, air-fried chips or mac and cheese.
Glaswegians have been flocking to try the £6.50 sandwich at the Serenity Now Cafe, Glasgow.
Amelia Sulhunt, 35, head chef, said: “We take a lot of inspiration from American vegan cuisine, and it’s not unusual to see soft drinks like Coca-Cola or Dr.Pepper being used in those dishes, so we started thinking about how we could put a Scottish spin on that, which inevitably led us to Irn Bru.
“It might sound a little strange at first, but Irn Bru is one of those soft drinks that has a very distinctive taste, so if you combine it with the right flavours, there’s a lot of possibilities there.
“Suffice to say, after we roasted our first batch, we were impressed enough to want to add it to the menu.”
Barry Nicolson, Serenity Now Cafe manager, hopes their customers will enjoy it.
The 34-year-old said: “We hope they’ll love it.
“We made a small trial batch a few weeks ago and had it on as a special, and the response was great - we sold out of it pretty quickly.
“We’ve been open for about a year now, so we wanted to change things up a bit and keep the menu interesting for our customers.
“It’s one of four new sandwiches we’ll be adding to the menu.”
The sandwich will form part of the cafe’s coming winter menu -- which will be in place at the beginning of November.
Approx calorie count BBQ sauce = 172 calories (100g).
Rocket = 4 calories (handful) Vegan cheese = 50 calories Pickles = 11 calories (100g) Irn Bru = 138 calories (330ml) Sourdough bread = 289 calories (100g) Pulled BBQ jackfruit = 150 calories Mushrooms = 21 calories (1 cup containing 96g) Total = 835 calories