Inquire with the company first. Ask them if they want to hear your idea and offer to sign an NDA (nondisclosure agreement). If you're not interested in money or lawsuits, tell them in writing they can have your idea no strings attached if they want to use it. Don't just send the idea in unsolicited.

We don't allow apps that promote violence, or incite hatred against individuals or groups based on race or ethnic origin, religion, disability, age, nationality, veteran status, sexual orientation, gender, gender identity, caste, immigration status, or any other characteristic that is associated with systemic ...

We don't allow apps that contain or promote sexual content or profanity, including pornography, or any content or services intended to be sexually gratifying. We don't allow apps or app content that appear to promote or solicit a sexual act in exchange for compensation.