Fallout, Fallout 2, Fallout Tactics
Having an addiction to Nuka-Cola is simply another status, with literally no drawbacks.
In Fallout this addiction is refereed to as "Nuka-Cola Craving" while in Fallout 2 it is refereed to as "Nuka-Cola Reliance".
The player cannot become addicted to Nuka-Cola in Fallout 3. However, there are a number of non-player characters who seem to be addicted to the soda. Sierra Petrovita also may be addicted to Nuka-Cola Quantum, as well as the original Nuka-Cola.
The player can become addicted to Nuka-Cola Quantum.