SUPPORT for Patients and Communities Reauthorization Act of 2023 This bill reauthorizes through FY2028 programs and activities relating to mental health and substance use disorder services. Reauthorized programs and activities include programs that enable access to drugs or devices that temporarily reverse opioid overdoses, activities to support the capacity of laboratories to detect synthetic opioids (e.g., fentanyl), residential treatment programs for pregnant and postpartum individuals, and training and workforce development for providers of mental health and substance use disorder services. The bill also modifies certain requirements relating to the regulation of controlled substances and the provision of mental health and substance use disorder services, including by requiring (1) the issuance of federal guidance to support at-home safe disposal systems for drugs, (2) studies to evaluate the efficacy of opioid treatment through buprenorphine and methadone, and (3) evaluations of the use of certain block grants by states to treat individuals with serious mental illnesses.