Build the Wall and Fight Fentanyl Act of 2023 This bill establishes accounts to fund the construction of physical barriers along the U.S. southern border and to provide grants to address fentanyl abuse. These accounts shall be funded from the sale of assets belonging to cartels that have been seized by the Drug Enforcement Administration, U.S. Immigration and Customs Enforcement, or U.S. Customs and Border Protection. The bill defines cartel as (1) an organization with operations in Mexico and the United States designated as a significant transnational criminal organization; (2) certain named organizations, such as the Sinaloa Cartel and the Juarez Cartel; and (3) other organizations as designated by the President.