I can identify the taste of Coke Zero (or anything with artificial sweeteners) vs coke 100% of the time. They barely even taste similar to me. My wife can’t taste a difference at all.
(doesn't apply to Pepsi though - here the regular one also tastes bad now as it contains sweeteners as well, so I doubt I'd tell it apart from Pepsi Max unless trained beforehand - they're both gross, so I unfortunately had to switch to Coca-Cola for my occasional coke cravings)