This is what the Quackwatch website:

Who Funds Quackwatch?
Stephen Barrett, M.D.
February 1, 2021

Quackwatch is now maintained by the Center for Inquiry, a 501(c)(3) nonprofit organization that strives to foster a secular society based on reason, science, freedom of inquiry, and humanist values.

Some people wonder whether Quackwatch or my other activities are a “front” for the American Medical Association, the pharmaceutical industry, the “medical establishment,” food companies, or whomever else they might not like. Nearly every week I get e-mails accusing me of this—and worse. Quite frankly, the idea is preposterous.

Neither I nor any authors of articles on this site have any conflicts of interest.
I have no financial tie to any commercial or industrial organization.
My viewpoints are not for hire. Even if they were, none of my imaginary funders would actually have a reason to hire me.
Standard medicine and “alternative medicine” do not actually compete for patient dollars. Well-designed studies have shown that most “alternative” methods are used in addition to—rather than instead of—standard methods.
The cost of operating Quackwatch and its affiliated sites from 1997 through 2019 was only a few thousand dollars a year. If donations and other income fell below what was needed, the rest came out of my pocket. Since 2020, the sites have been hosted by the Center for Inquiry. I still have modest research expenses that are covered either by donations or by me.

As to the financing of the Center for Inquiry you can download their Annual Report from here: https://centerforinquiry.org/about/annual-reports/