London (CNN)It will come as no surprise that milkshakes loaded with sweets, chocolate bars, cream and cake, known as freakshakes, contain "grotesque levels" of sugar.
But now one campaign group wants them to be labeled with a nutrition warning and the worst offenders banned.
Action on Sugar, based at Queen Mary University of London in the UK, conducted a survey of 140 drinks at UK fast-food chains and restaurants and found they contained "alarming" levels of sugar and calories.
The "Unicorn Freakshake" sold by UK restaurant chain Toby Carvery was the worst of those surveyed, containing more than six times the recommended daily amount of sugar for children between the ages of 7 and 10.
At 1,280 kilocalories it contains more than half the recommended 2500 calorie intake for an adult.
"An average 25-year-old would need to jog for nearly three hours or vacuum the house for five hours to burn off the calories!" the group said in a statement.
The drinks are popular on Instagram, where the general rule is that the bigger the tower of sugary items, the more delicious the drink.
The next worst offender on Action on Sugar's list was Five Guys' banana and chocolate shake with 1,073 calories -- the equivalent of more than four cans of cola. The fast-food chain also took third position for its cherry milkshake, which has 975 calories.