May-Bowles, who calls himself Jonnie Marbles, admitted assault and causing harassment, alarm or distress.
The stand-up comic was sentenced at City of Westminster Magistrates' Court.
Mr Murdoch and his son James were giving evidence before MPs at the Commons Culture, Media and Sport Committee on 20 July when May-Bowles rushed forward from the public gallery with a paper plate filled with foam.
The substance hit the 80-year-old's jacket.
After pleading guilty to the offences last week, the part-time comic told reporters, "I would just like to say this has been the most humble day of my life", mimicking Mr Murdoch's statement to the MPs.