"I mean, Marco Rubio, as an example. He's got no money, zero. Now, I think that's OK, (but) ... I mean, he's got nothing," said Trump, speaking before the Greater Charleston Business Alliance at a joint event with the South Carolina African-American Chamber of Commerce in North Charleston, South Carolina.
Trump -- who is often mocked for his own signature coif -- even went after Rubio's hair.
"(Rubio) announced he was going to run because he's overly ambitious, too young -- and I have better hair than he does, right?" Trump said to cheers from the crowd.
Rubio's campaign declined to comment beyond the Florida senator's appearance on Fox News Tuesday, when he said Trump was not ready to serve as commander-in-chief
given Trump's sparse foreign policy knowledge.
Trump has consistently attacked his Republican presidential rivals as they rise in the polls, including former Florida Gov. Jeb Bush and former Hewlett-Packard CEO Carly Fiorina, and the ascendant Rubio is his latest target
Trump was apparently in a fighting mood, after declaring a boycott of Fox News earlier in the day
. And Rubio wasn't his only target: few rivals were spared from his attacks.
Trump riffed extensively on the perspiration of other candidates during last week's CNN-hosted debate.
"That room was hot. I mean, poor Chris Christie!" he said. After some gasps and laughter, Trump said, "No, it's true."
"(Christie)'s a nice guy. It wasn't fair. it was an amazing thing; I was like a piece of water," he said.
Rubio was again mocked, with an oblique reference to his infamous gulping of water during his 2013 State of the Union GOP rebuttal.
"Rubio -- I've never seen a young guy sweat that much. He's drinking water, water, water. I never saw anything like this with him with the water," Trump said.
Former Arkansas Gov. Mike Huckabee?
"A nice guy ... was seriously hot," Trump said. "I grabbed him around his back ... and he was soaking wet. He was drenched."
Trump also took on Fiorina, who, like Rubio, gained in CNN/ORC's latest poll
"Her business career was a disaster and nobody wants to say it," he said. "They say, 'You can't say that because it's sexist.' I say, what's sexist about it?"
"I respect women more than I respect men," Trump added.
He then turned to attacking Democratic front-runner Hillary Clinton, who he said has pushed back on his comments about women.
"Hillary, who's become very shrill -- you know the word shrill?" Trump said. "She's become shrill."
The event, which Trump said he had only given potential attendees 10 minutes notice for, was sparsely attended, one of the lowest turnouts for his campaign thus far. And despite his claim it was a surprise, his attendance at the conference was publicized
as early as Sept. 11.