The new bottled beverage, which goes by the trendy yet unpronounceable name of CLR CFF (or "clear coffee" devoid of vowels), was developed by two Slovakian brothers who were bothered enough by how regular coffee was staining their teeth that they came up with a recipe for one that lacks any color at all. They won't reveal exactly how it's made, but say it took them three months to perfect the method and is "based on physical processing." They also claim it doesn't involve any weird chemicals, stabilizers, sweeteners, or additives, and that it's derived from freshly roasted Arabica beans. The only ingredients listed on its site are water, fresh coffee and caffeine, and a 200ml bottle packs 4 calories (a 200ml serving of regular black coffee typically has just 1).
As for how it tastes, opinions are mixed. According to the Evening Standard, the taste is "strong, like a potent cold brew," while employees at Metro who tried it described it varyingly as "odd, but not unpleasant" and like "Water…but an aftertaste of coffee." It's also a bit of a stretch to claim that it's totally colorless, since it has a very slight yellow/brownish tint.