The tete-a-tete went down after a performance from the death-defying escape artist Demian Aditya, whose insane stunt was marred by technical difficulties that essentially ruined the trick and left the judges underwhelmed.
"I kind of imagine this would be like Mel B's wedding night," Cowell began when it was his turn to give feedback. "A lot of anticipation, not much promise or delivery."
Before he could get to his punchline, the 42-year-old singer -- who is in the middle of a contentious divorce with her ex, Stephen Belafonte -- stood up and aggressively threw her cup in Cowell's face, soaking his shirt and hair, before storming off stage.
This isn't even the first time this season Mel's thrown her drink at her fellow judge. During the audition rounds, Cowell joked that she'd managed to get famous without knowing how to dance and ended up getting soaked.
See photos of the "America's Got Talent" judges:
2017 'America's Got Talent' judges
2017 'America's Got Talent' judges
AMERICA'S GOT TALENT -- 'Live Finale Results' Episode 1224 -- Pictured: (l-r) Mel B, Howie Mandel, Heidi Klum, Tyra Banks, Simon Cowell -- (Photo by: Trae Patton/NBC/NBCU Photo Bank via Getty Images)
AMERICA'S GOT TALENT -- 'Live Finale Results' Episode 1224 -- Pictured: (l-r) Howie Mandell, Mel B, Simon Cowell, Heidi Klum -- (Photo by: Trae Patton/NBC/NBCU Photo Bank via Getty Images)
"When you lose somebody, you don't really expect to be in the same situation as somebody else when you're on live TV, and they're going through the same thing," she shared. "So when her story came up again, I'm like, 'Oh my gosh, that's very similar to mine.' I wanted to put the story aside and just focus on her voice, but it all just collided. Thank god she has such a beautiful voice."
See photos of Simon Cowell through the years:
Simon Cowell through the years
Simon Cowell through the years
Simon Cowell during Record of the Year 2001 at Hard Rock Cafe in London, United Kingdom. (Photo by Fred Duval/FilmMagic)
The Brit Awards 2002', Earls Court, London, Britain - 20 Feb 2002, Zoe Ball With Simon Cowell (Photo by Brian Rasic/Getty Images)
(Left to right) FOX's American Idol judges Simon Cowell, Paula Abdul and Randy Jackson pse peaceably at the FOX 2002 SummerTCA Tour at the Huntington Ritz Carlton Hotel in Pasadena, CA on Monday, July 22, 2002. Photo credit: Kevin Winter/ImageDirect
Simon Cowell with a Wilson's leather bag during The 2002 Teen Choice Awards - Backstage Creations Talent Retreat - Day 1 at Universal Amphitheatre in Universal City, California, United States. (Photo by L. Cohen/WireImage)
Simon Cowell, Paula Abdul and Randy Jackson at 'The Teen Choice Awards 2002' at the Universal Amphitheatre in Los Angeles, Ca. Sunday, August 4, 2002. Photo by Kevin Winter/Getty Images/FOX.
Simon Cowell during Paula Abdul, Simon Cowell, and Christina Christian of American Idol Leave MTV's TRL - August 18, 2002 at Times Square in New York City, New York, United States. ***Exclusive*** (Photo by James Devaney/WireImage)
Randy Jackson & Simon Cowell during 'American Idol' Season 1 Finale - Results Show - Press Room at Kodak Theatre in Hollywood, California, United States. (Photo by Gregg DeGuire/WireImage)
Paris Hilton and Simon Cowell during Scary Movie 3 Los Angeles Premiere - After Party at The W Hotel in Westwood, California, United States. (Photo by Jeff Kravitz/FilmMagic)
Simon Cowell during Simon Cowell Signs Copies of His New Book, 'I Don't Mean To Be Rude But...' at Barnes And Noble, Rockefeller Center in New York City, New York, United States. (Photo by Debra L Rothenberg/FilmMagic)
BURBANK, CA - JANUARY 19: 'American Idols' judge Simon Cowell (left) appears on 'The Tonight Show with Jay Leno' on January 19, 2004 at the NBC Studios, in Burbank, California. (Photo by Kevin Winter/Getty Images)
Matt Rogers and Simon Cowell during 'American Idol' Season 3 - Top 12 Finalists Party - Inside at Pearl in Los Angeles, California, United States. (Photo by SGranitz/WireImage)
Simon Cowell during 102.7 KIIS-FM's 'Wango Tango On-Air' Concert 2004 at Rose Bowl in Pasadena, California, United States. (Photo by J. Shearer/WireImage)
Simon Cowell and Paula Abdul (Photo by Ray Mickshaw/WireImage)
HOLLYWOOD - APRIL 20: Television host Ryan Seacrest poses with American Idol judges (L-R) Paula Abdul, Simon Cowell and Randy Jackson, after receiving a star on the Hollywood Walk of Fame on April 20, 2005 in Hollywood, California. (Photo by Frazer Harrison/Getty Images)
Simon Fuller, creator of 'American Idol', Carrie Underwood, winner of 'American Idol' Season 4 and Simon Cowell (Photo by Ray Mickshaw/WireImage)
'American Idol' judge Simon Cowell and Terri Seymour (Photo by SGranitz/WireImage)
Simon Cowell and Paula Abdul (Photo by Denise Truscello/WireImage)
THE TONIGHT SHOW WITH JAY LENO -- Episode 3313 -- Pictured: (l-r) 'American Idol' judge Randy Jackson, host Ryan Seacrest and judge Simon Cowell during an interview on February 19, 2007 (Photo by Paul Drinkwater/NBC/NBCU Photo Bank via Getty Images)
THE TONIGHT SHOW WITH JAY LENO -- Air Date 1/21/08 -- Episode 3480 -- Pictured: Television personality Simon Cowell during an interview on January 21, 2008 (Photo by Paul Drinkwater/NBC/NBCU Photo Bank via Getty Images)
NEW YORK - NOVEMBER 22: Executive producer and TV personality Simon Cowell displays his Founders award in the press room during the 38th International Emmy Awards at the New York Hilton and Towers on November 22, 2010 in New York City. (Photo by George Napolitano/FilmMagic)
LONDON, ENGLAND - DECEMBER 09: (L-R) Liam Payne, Louis Tomlinson, Harry Styles, Zane Malik and Niall Horan of 'One Direction' together with Simon Cowell (c) attend a photocall during the X Factor press conference at the Connaught Hotel on December 9, 2010 in London, England. (Photo by Ian Gavan/Getty Images)
THE TONIGHT SHOW WITH JAY LENO -- Episode 4000 -- Pictured: (l-r) TV personality Simon Cowell during an interview with host Jay Leno on March 2, 2011 (Photo by Paul Drinkwater/NBC/NBCU Photo Bank via Getty Images)
Simon Cowell attends 'The X Factor' auditions at Bank United Center on June 14, 2011 in Miami, Florida. (Photo by Vallery Jean/FilmMagic)
JIMMY KIMMEL LIVE - 'Jimmy Kimmel Live' airs every weeknight, (12:00 - 1:06 a.m., ET), following 'Nightline,' featuring a diverse lineup of guests that include celebrities, athletes, musical acts, comedians and human interest subjects, along with comedy bits and a house band. The guests for TUESDAY, SEPTEMBER 20 included Simon Cowell ('The X Factor') Ron Artest and Peta Murgatroyd ('Dancing with the Stars' cast off) and musical guest Gavin DeGraw. (Photo by Carin Baer/Disney XD via Getty Images)SIMON COWELL, JIMMY KIMMEL
LOS ANGELES, CA - DECEMBER 19: Simon Cowell and Melanie Amaro attends 'The X Factor' press conference at CBS Television City on December 19, 2011 in Los Angeles, California. (Photo by Jeffrey Mayer/WireImage)
LONDON, UNITED KINGDOM - APRIL 11: Alesha Dixon, Simon Cowell and Amanda Holden attend the press launch for the new series of 'Britain's Got Talent' at ICA on April 11, 2013 in London, England. (Photo by Stuart C. Wilson/Getty Images)
LOS ANGELES, CA - NOVEMBER 04: Simon Cowell arrives at 'The X Factor' finalists party held at SLS Hotel on November 4, 2013 in Los Angeles, California. (Photo by Michael Tran/FilmMagic)
MIAMI BEACH, FL - FEBRUARY 24: Simon Cowell and Eric Cowell are sighted on the beach in Miami Florida. on February 24, 2014 in Miami Beach, Florida. (Photo by Dave Lee/GC Images)
MIAMI, FL - MARCH 03: Simon Cowell is seen as he gets on a Vespa for a scooter ride on March 03, 2014 in Miami, Florida. (Photo by Radcliffe/Bauer-Griffin/GC Images)
LONDON, ENGLAND - MARCH 26: Lauren Silverman and Simon Cowell attend the press night of 'I Can't Sing! The X Factor Musical' at London Palladium on March 26, 2014 in London, England. (Photo by Karwai Tang/WireImage)
LONDON, ENGLAND - FEBRUARY 24: Simon Cowell with his Outstanding Contribution to Entertainment award and Lauren Silverman during the Elle Style Awards 2015 at Sky Garden @ The Walkie Talkie Tower on February 24, 2015 in London, England. (Photo by Gareth Cattermole/Getty Images)
LONDON, ENGLAND - JULY 21: Simon Cowell arrives at The X Factor Auditions at Wembley on July 21, 2015 in London, England. (Photo by SAV/GC Images)