Humanitarian Standards for Individuals in Customs and Border Protection Custody Act This bill imposes requirements and standards related to the care of aliens in U.S. Customs and Border Protection (CBP) custody. CBP shall conduct an initial health screening of each alien in custody to identify those with acute conditions and high-risk vulnerabilities and to provide appropriate health care. CBP shall conduct the screening within 12 hours of each alien's arrival at a CBP facility, and within 6 hours for certain priority individuals such as children, pregnant women, and those with disabilities. The bill imposes various requirements related to the services, personnel, and infrastructure for providing such screenings, such as providing interpreters, chaperones, and mental health treatment when necessary. CBP shall ensure detainees have access to drinking water, toilets, sanitation facilities, hygiene products, food, and shelter. The bill imposes certain standards relating to such requirements, such as the minimum amount of drinking water for each detainee and the acceptable temperature range of the shelters. The Department of Homeland Security (DHS) shall enter into memoranda of understanding with various emergency government relief agencies to address instances when surge capacity is necessary. The Inspector General of DHS shall conduct unannounced inspections of ports of entry, border patrol stations, and detention facilities and report the results to Congress. The Government Accountability Office shall assess CBP management of such facilities and whether CBP and DHS processes are in compliance with this bill's requirements.