Always Coca-Cola?

That’s the way it is at a Manhattan office building owned by the Coca-Cola Co. – which apparently can’t stand the thought of tenants or visitors walking around with Pepsi products.

Two Post reporters who brought bottles of Diet Pepsi into the lobby at 711 Fifth Ave. were admonished by security guards – who take the company slogan very seriously.

“Hey, you shouldn’t have that in here,” one guard said when he spotted the rival soft drink.

Building employees said the security guards get a lecture if Coke bigwigs who work upstairs spot someone drinking Pepsi in the lobby.

Messengers who bring in a Pepsi are offered a fresh Coke or a Coke cup so that no one will see the offending brand, they said.

You won’t find Pepsi products in the non-Coke offices, either.

“Within our own law firm, out of respect and admiration of our friends [at Coke worldwide headquaters] in Atlanta, we don’t bring in carbonated beverages other than Coca-Cola products,” said Robert Werbel of the law firm Heller Ehrman White and McAuliffe, which leases a floor from Coke.

Coca-Cola spokesman Bill Hensel said the building’s leases ban vending machines or coolers from the competition, but he insisted individuals are free to drink what they want.

Pepsi spokesman Jeff Brown disagrees. “We see this kind of attitude all the time. Coke wants to force everybody into a nightmarish world where it’s always Coca-Cola – or else,” he said.

Brown – who said visitors are free to drink Coke at Pepsi plants – recalled the case of Mark Cameron, who was suspended for wearing a PepsiT-shirt to his Atlanta high school on Coke Day.

“They’re really uptight,” he said. “And not just in New York.”