Apparently, they taste like "sweet lemon lime chips."
The move is probably not a huge surprise as Frito Lay is the same company that introduced Pepsi-flavored Cheetos last year.
Stranger still, this isn't the first Mountain Dew-flavored snack put out by Frito Lay. Back in 2008, they came out with a mystery flavor of Doritos chips that turned out to be Mountain Dew flavor... here in the US!
If you're looking to try Mountain Dew Cheetos, there are a few online Japanese import specialty stores that offer them including this one, which has them going for $3.50 each.