Why would pepsi cans spell "sex" tho.? What would they gain from it? If I were going to print subliminal message on pepsi cans they would read "buy pepsi" or "drink pepsi", not "sex".
"Sell pepsi" seems kind of obvious. Sex makes it look like a more attractive deal, even though it's pepsi they're selling in the end. This has been going on for a long time in all kinds of marketing; instead of painting the factual benefits of a product you try to communicate a feeling or a sort of achievement you want to associate the product with. Seems to work.