The sweetest rum to drink straight is subjective and can vary depending on personal taste, but some of the most popular sweet rums include Diplomatico Reserva Exclusiva, Ron Zacapa 23, and Zaya Gran Reserva. Diplomatico Reserva Exclusiva is a Venezuelan rum that is known for its rich and sweet flavor with notes of toffee and vanilla. Ron Zacapa 23 is a Guatemalan rum that is aged in a unique aging process and is known for its smooth and complex flavor profile with notes of caramel and chocolate. Zaya Gran Reserva is a Trinidadian rum that is aged for 12 years and is known for its sweet and spicy flavor with notes of vanilla and cinnamon. Other popular sweet rums include El Dorado 12-Year-Old, Pyrat XO Reserve, and Plantation XO 20th Anniversary. (source: The Manual, VinePair)