There were two different
formulas of Crystal Pepsi. The original formula was more akin to regular Pepsi with less sugar and no
caramel. Imagine the same flavors as
Pepsi with the less-citrusy
signature of
Coke.
The second formula was sweeter and put a much larger emphasis on the citrus flavors (some of which weren't present at all in the first formula).
As I recall, Crystal Pepsi had been deemed a commercial failure, almost identical to the way New Coke failed. The change in formula was an attempt to breathe life into the product line, but unfortunately the pop culture contempt for the drink, and its lasting status as a joke food 1 had killed any chance of survival for any product with that name. The second formula didn't last long before the product was discontinued.
1See the song "Why is everybody picking on me" by the Bloodhound Gang.