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 Lithuania.
It is prohibited to sell, serve or supply alcohol beverages to anyone under the age of 20 years. People under the age of 20 are prohibited from consuming alcohol beverages or from possessing them. The minimum age was raised from 18 to 20 in 2018.
You can find more legal details and links here:
Wikipedia Legal Drinking Page