Bayern's coach snubbed Porter's attempted handshake following last week MLS All-Star Game in Portland with Guardiola blaming the American tactician for a number of tough tackles against the visitors from Bavaria.
While Porter, coaching the representative team, looked sick as Guardiola furiously remonstrated with him during the second half and after the game at Portland's Providence Park on Wednesday, the 39-year-old seemed to have seen the humorous side by Monday.
In a video posted on social media to raise awareness for Amyotrophic lateral sclerosis (ALS) - also known as Lou Gehrig's disease - Porter accepted the Ice Bucket Challenge, where a bucket of ice water was tipped over his head, and then challenged Guardiola to be next.
Porter had been challenged by former United States international and football analyst Taylor Twellman.
"I in turn challenge [United States women's national team player] Alex Morgan, [sports journalist] John Canzano, [United States coach] Jurgen Klinsmann and Pep Guardiola," Porter said, miming a handshake as he said the Spaniard's name.
The Ice Bucket Challenge has reportedly raised $1.35 million for the ALS Association since the campaign started on July 29.
During the second half of the MLS All-Star Game Osvaldo Alonso and Will Johnson - who were representing the American league - slid into Bayern's Xherdan Shaqiri and Bastian Schweinsteiger respectively.
Guardiola was livid following the two tackles, ranting at the referee, the fourth official and Porter - with the latter looking very apologetic for the behaviour of his players.
After the game, Porter attempted to approach Guardiola to shake his hand but the former Barcelona coach wagged his finger in refusal before again unleashing his anger at the referee and his assistants.
