Jägermeister in his hip flask containing rum – which would have resulted in a burning – The Duke of Cambridge Jäger Bomb.
Prince William toasted with a sip of a small silver bottle at the Middle of the Temple at Embankment, London.
However, the drink could have been harder to swallow than he had imagined, as the 36-year-old prince tried to explain himself.
When asked if he had bought a drink, the prince said: "I'll never drink twice, it's very important.
READ MORE: Prince William lays poppy wreath to honor fall submariners at Remembrance parade
"They tried to put a Jägerbomb in it! Imagine my surprise – burnt my throat. "
The memory of the prank stayed with Prince William throughout the day, as he spoke about it later on.
During the reception, while he was chatting with guests, the third-in-line to the throne
He said: "They tried to put hunter bomb instead of rum – that would have sorted me out, I was expecting rum and got a hunter."
During the annual service in memory of Submariners who lost their lives was in a Prince William laid a remembrance wreath at the foot of the military drums on display, before stepping back to pay his respects by bowing his head.
He was rehearsing in the Royal Air Service (RAF), together with a red remembrance poppy.
Prince William was admitted to the Royal Military Academy at Sandhurst in January 2006.
Three years later, he was transferred to the RAF and promoted to Flight Lieutenant.
He served as a pilot until July 2017, when he left the Army to assume responsibility for his grandmother, the Queen.
Embankment became the venue for the Submariners' Remembrance Service and Parade in 1923, after which the Silent Service was placed between Blackfriars Bridge and Waterloo Bridge.
The stunning statue depicts a submarine crew, Truth and Justice in human form, 40 anchor-shaped wreath hooks.
And it lists the submarines lost in the two World Wars.
William's royal engagement represented just one of the many ceremonies and this coming week to honor the victims of all wars.
Next Sunday, on November 11, the National Service of Remembrance will be held at the Cenotaph on Whitehall, in London.
Last year, Prince Charles, Prince Philip.
Prince William's wife Kate, the Duchess of Cambridge, paid a visit to London's Imperial War Museum, on the opposite side of the Thames.
There, the duchess saw letters about three brothers of great-grandmother, all of whom fought and died in action within the first two years of the World War I.