Strictly addressing fermentation, which is the action of bacteria on sugar, the pH of the stomach varies two points either side of 3, quite acidic, not a viable environment for bacteria to perform fermentation.
The bogus advice has been around for many, many years. The common Internet version is to eat fruit on an empty stomach, because it will then be properly absorbed. If there's anyone who might reasonably choose when to eat their fruit, it would be diabetics, and they might get some benefit from doing the opposite, eating other foods with their fruit, to slow absorption, although fructose is the least troublesome of sugars.
"Kitchen duty is awarded only to those of manifest excellence..." - The Master, Dogen