Red Bull vs. Red Bull Sugar Free
This question is irrelevant to those who think that Red Bull in any incarnation tastes "gross". Happily, I like the taste of Red Bull. I've liked it ever since my first tiny can at a Bavarian water park when I was 13.
Then, as now, the component of the flavor that strikes me the most, the part that is unique among soft drinks, is the "nose". Nose is a term commonly reserved for drinks like wine and beer because of the way alcohol fumes travel into the sinuses after sipping. Red Bull, however, has a distinct nose.
I liken Red Bull's nose to the fumes one experiences when eating circus peanuts or anything with artificial banana flavor in it. It's a sweet funk that hangs in the back of your throat and sinuses. I think it's great, but I can understand how such a description might send others running.
The question, luckily, is not whether Red Bull is any good, but how Red Bull Sugar Free compares to the original. Does it maintain those distinct Red Bull attributes like the "nose"? Let's review my completely subjective notes.
The aforementioned "nose" is strong but not overpowering. There is the slightly chemical citrus taste that hints at a lemon scented cleaning product. These highlights, in combination with the perfect level of carbonation (very slight), give Red Bull that wonderful taste that my slightly synesthetic brain perceives as "round". (and yes, the number three is green and bass notes taste like teriyaki)
Red Bull Sugar Free
The "nose" I like in the original Red Bull is much reduced in the Sugar Free version. Perhaps that part of the flavor is tied strongly to the sugar and doesn't manifest as well with sucralose? It is approximately as citrus flavored in that chemical way, but instead of the "round" impression I get from the original, Sugar Free has an astringent sharp taste underneath the citrus and is far more carbonated. It's a little reminiscent of tonic water. It's spiky, not round.
Red Bull Sugar Free isn't awful, it's just not as good. And to its credit, the difference in taste between the two is not nearly as great as the difference between regular and diet versions of other soft drinks.