Coca Coca spends about $3 billion a year on advertising.  I couldn't find a breakdown for how much is brand-building versus other goals, but I think we can agree it's a lot.
That suggests two hypotheses: A) People in charge of a $3 billion budget for an incredibly profitable and long-lived company know what they're doing, or B) An anonymous non-expert on the Internet has correctly realized that advertisers are just fooling themselves, and he (and everybody else) is above being manipulated by brand advertising.
No offense, but I'm going with A.
On a personal note, I grew up drinking Coke (because my dad preferred it), and I generally prefer the taste of Coke most likely because it's what I grew up drinking. I've seen Coke ads, and I've seen Pepsi ads, and neither one makes me want to drink one or the other or go buy one or the other. About the only thing it might do is influence me to go get a Coke if I was already feeling a bit thirsty although even if it was a Pepsi ad it would probably still make me want to get a Coke. In this case it would be a win for Soda vs. some other kind of drink like say a Starbucks coffee, not specifically Coke vs. Pepsi.
See the first reply to the first post:
> Holy fuck. You're right. I bought a car recently, and while the TV spots had nothing to do with my decision, now when I see them, I sing along with the song and cheer at the TV and shit.
It turns people who bought your product in to people who are fans of your product, which makes them more likely to become repeat purchasers (and less likely to seriously consider other brands when it's time to purchase).