Register a company, say you did freelance consulting work in the gap. Can't disclose details due to NDAs, but it's fascinatingly close to the core competencies of the place you're applying to.
If a company reads it and doesn't like it, then they don't like it. You are looking for the one who accepts your resume.
I personally have started a company, and legit spend 9 months just researching and decided not to do it. Nothing wrong with that.
I don't understand why people think it's okay to outright lie on your resume.