Here lists the time Cartoon Network aired marathons for the show.
The first marathon being on Sunday, January 21, 2007 at 6 pm.
The second one being before Season 2's premiere; titled, the Sing Along with Sunny Musical Marathon which aired on Thursday, June 7, 2007.
Sunny Musical Marathon (2007)
Cartoon Network January 2007 Class of 3000 Marathon Tomorrow at 6 pm on Cartoon Network