This research study is testing a new behavioral therapy called Episodic Future Thinking or EFT can help people reduce drug use and risky sexual behaviors while helping them adhere to their HIV prevention medication (PrEP). Participants will be randomly assigned to one of two groups. One group will receive standard care, which includes counseling on HIV prevention, drug use reduction, and sexual health. The other group will receive standard care plus a new program called Episodic Future Thinking (EFT), where participants will think about and plan for their future goals using a mobile app and counseling sessions. Study procedures that are not part of regular care include filling out surveys, providing blood, urine, and swab samples for testing, and using the EFT app.