If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Benin.
Republic of Benin Report to UN Committee on the Rights of the Child CRC/C/BEN/2 (2005): Article 8 of the decree of 10 June 1942 regulating the production, import, advertisement, sale, and consumption of alcohol beverages in French West Africa, prohibits the sale or free supply of alcohol beverages to minors under 20. Article 13 stipulates fines ranging from CFAF 200,000 to CFAF 1 million for such offences, doubled in the case of repeat offences. There are no official measures prohibiting children from consuming alcohol, tobacco or other substances harmful to their health.
You can find more legal details and links here:
Wikipedia Legal Drinking Page