i have facebook page with 1 million likes struggling to get sponsors my page category is in health niche
just do your pramotion on comments section in other websites like linkedin, instagram, and facebook too
One of the possible approaches: Make the analysis of Your targeted audience that subscribed to Your Great Page or visit Your page regularly. After that, You will get a clue which potential sponsors might be interesting in Your offer (being Sponsor). You can reach them via Socla Media or just e-mailing them with offer of cooperation.