I found this article fascinating...

Official: Coke takes over parts of the brain that Pepsi can't reach

An excerpt:

Simply looking at a person's brain scan, the scientists were able to predict which soft drink the individual concerned was likely to prefer. "We were stunned by how easy this was," Dr Montague said. The ventral putamen, which is involved in reward-related learning, was active when people drink Coke or Pepsi. This is expected as the brain treats the pleasant taste of sugared water as a reward.

However, the scans also showed that the hippocampus and dorsolateral prefrontal cortex, areas of the brain involved in recalling emotions and cultural memories, were involved when the volunteers were exposed to the Coke brand. The Pepsi brand, meanwhile, had virtually no effect.

Note:  I usually mark posts which are totally off-topic with the [OT] prefix; you can ignore these if you are looking for technical content