Competition is driving many fast food restaurants to allow customers to order off menu, building their own personally tailored burger, soft serve and burrito combinations. The resulting "secret menu" items are often shared on social media by "food hacking" enthusiasts keen to show off their new creations.

HackTheMenu.com compiles some of the best (and worst) popular secret menu items from larger chains including McDonald's, Burger King, Subway and KFC.

Below are ten hits and misses that are proving popular around the world:

McDonalds: Monster Mac

"He did the Mac... He did the Monster Mac..." http://t.co/TxYIgChjkf pic.twitter.com/PJHNKW4VqU — Burger Lad (@Burger_Lad) December 21, 2013

The Monster Mac has all the regular Big Mac toppings, but features eight beef patties crammed between three layers of dough.

Burger King: Frings

"@LifeCheating: Life cheat for Burger King: pic.twitter.com/kQsJ64dXYl" If you live in Nebraska, you should know what Frings are... #Runza — Logan Berggren (@logs_arithm) April 29, 2014

The "perfect" combination of french fries and onion rings, available at Burger King.

Starbucks: Cotton Candy Frappuccino

A vanilla bean frappuccino with extra raspberry syrup.

McDonalds: McCrepe

10 Secret Menu Items You Can Order at Fast Food Restaurants - MCDONALD'S MCCREPE http://t.co/28JM8Dxhqb via @PeopleMag — Kristin Grace (@BKristin_Grace) September 24, 2014

A McDonalds pancake covered in yoghurt parfait and topped with granola and syrup.

KFC: Poutine

KFC/A&W secret menu item unlocked! Poutine! pic.twitter.com/bJRnVwfzvx — Daniel Dawson (@spectre615) September 4, 2013

A reproduction of the popular Canadian fast food with french fries and cheese curd, sometimes served with chunks of chicken and then smothered in gravy.

Subway: Pizza Sub

@Wintergore is a genius! #Subway pizza sub, double cheese added BEEF! Olives. Green Peppers and onions! All toasted pic.twitter.com/REw2S4QGCc — BARRICADE (@zxBARRICADExz) August 15, 2014

A regular subway sub with spicy pepperoni, tomato Sauce, cheese and toppings to taste.

Starbucks: Twix Frappuccino

Sometimes it's all I need... Twix frappuccino. pic.twitter.com/hgbJmEbO8N — Cruz (@vivvdaily) October 21, 2014

A caramel frappuccino with extra caramel and hazelnut syrup plus java chips and caramel & mocha drizzle.

McDonalds: Mc10:35

Came to McDonald's at the perfect time. This is called the Mc10:35 pic.twitter.com/p3EjF6O0Qw — Ian Oliver (@EeyanOliver) October 24, 2013

The Mc10:35 is only available in the brief cross-over window between breakfast and lunch when McDonalds will serve an Egg McMuffin with two burger patties jammed inside it.

In N Out: Well Done Fries

I haven't had a 4x4 with a toasted bun and well done fries pic.twitter.com/YGmeqSPCUA — JulJin (@julianpowpow) October 22, 2014

Like regular fries, but cooked for longer to make them crispier.

Burger King: Suicide Burger

Burger King's "Suicide Burger". Heaven and a smile inside of a sesame seed bun. Why keep it a secret? #SecretMenuItem pic.twitter.com/b3kEN9NucI — Secret Menu Items (@SecretMenuItem) April 18, 2014

Four beef patties, four slices of cheese, bacon and special sauce.

And for dessert, presumably, a heart attack.

Main photograph by Burger Lad.