 Fat Brands Inc. , owner of such restaurant chains as Fatburger and Ponderosa, said Thursday it had agreed to buy the Johnny Rockets restaurant chain from the private equity firm Sun Capital Partners for about 25 million. The acquisition will be funded through cash on hand and proceeds generated from the companys securitization facility, Fat Brands said. Once the acquisition is completed, Fat Brands said it will have more than 700 franchised and company-owned restaurants around the globe with annual system-wide sales exceeding 700 million. 