None of the job titles listed (apparel graphic designer, logo designer, multimedia designer, publication designer) typically include the specific role of a brand ambassador. A brand ambassador generally focuses on representing and promoting a brand's image and products, often through marketing, social media, or public relations efforts. However, a job in marketing or public relations would be more directly related to the duties of a brand ambassador.
If you must choose from the given options, none fits the job responsibility perfectly, but a multimedia designer might have some overlap if their work involves promotional content for the brand.