Marketers should have known  don't mess with consumers' sentimental attachment to a product. Especially when it's 99-year-old Coca-Cola. The "newer, sweeter" version, introduced April 23, 1985, succeeded in blind taste tests but flopped in the real world. Phone calls, letters and rants from Coke die-hards flooded in, and just three months after its debut, New Coke was removed, and the word Classic was added to all Coke cans and bottles to assure consumers they were getting their first love.

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