Not every item that can be ordered appears on a menu board. Image source: McDonald's.

In some ways, secret menus have become less secret over the last few years.

More consumers know what they are and some chains, like In-N-Out Burger, have embraced them. Basically, a secret menu consists of items that can be ordered but do not appear on the normal menu board.

That does not mean you can order prime rib at a Starbucks (SBUX 0.72%). In general, the non-public items involve ingredients that are used by the chain in combinations other than the intended ones. At the coffee chain, that means using syrups, toppings, and extras to create new flavors.

In many cases, you can order secret menu items, and the person behind the counter will know what you want. Order a Birthday Cake Frappuccino, for example, and many baristas will know what to do, as that item has become a commonly ordered secret item. Request a Stormtrooper Frappuccino, however, and you had best be prepared to lay out the ingredients.

There's no guarantee that a McDonald's (MCD 0.07%) or Restaurant Brands International's (QSR 0.46%) Burger King will honor an off-menu request, but both chains have well-established secret menus. Here's what people in the know are ordering.

What's on McDonald's secret menu?

Compared to most chains, McDonald's has a very limited secret menu, with two main off-menu items to choose from, according to

There's the "Land, Air, and Sea Burger," which features all the ingredients of a Big Mac, a McChicken, and a Filet-O-Fish served together in one big sandwich. The chain also has the be-careful-how-you-state-your-order McGangBang, a McChicken sandwiched inside a double cheeseburger.

Some order takers will know these by name, but most will let you order them as "grill orders" if you specify the ingredients. A grill order is any menu item not ordered exactly per normal specifications, which could mean asking for extra pickles or, in this case, laying out the ingredients for the Land, Sea, and Air Burger.

Of course, these are not the only secret menu items at McDonald's, only the most famous. HacktheMenu has a list of lesser-known McSecrets like the Monster Mac and the McCrepe that some stores may be willing to make for you.

What's on Burger King's secret menu?

Once a chain puts Mac 'n Cheetos on its actual menu, it's hard to imagine that there's anything it won't do. Burger King has a very involved secret menu, according to Much like McDonald's secret items, these are all combinations of existing ingredients combined to form something new. Some favorites include the Burger King BLT, which is a Whopper with bacon added as a topping, and the Chicken Club, a traditional chicken sandwich with bacon, tomato, and cheese added.

Another popular secret menu choice has been dubbed "Frings" by its fans. This is simply a half order of French fries mixed with a half order of onion rings. In addition, Burger King patrons can order the Rodeo Burger -- a onetime regular menu item that was dropped -- by asking for barbecue sauce and onion rings on a regular hamburger.

And if you like Burger King but hate yourself, you can ask for the Suicide Burger -- a monstrosity featuring four beef patties, four slices of cheese, bacon, and special sauce served between two sesame seed buns.

Why do secret menus matter?

Secret menus can build loyalty by making some customers feel like part of a secret club. That said, neither Burger King nor McDonald's has done a particularly good job of leveraging its secret menu. Starbucks has been a leader in this area, not only embracing the idea of letting consumers concoct their own drinks but even moving a few of them over to the actual menu.

The two leading burger chains have not embraced the trend, leaving it up to customers to figure out these innovative food combinations. Ordering a Land, Air, and Sea Burger or a Rodeo Burger is much harder than it needs to be.

Secret menus can be a way to build stronger relationships with your best customers. In these cases, both chains are mostly letting that opportunity slip by.