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 Sweden.
See also: Alcohol in SwedenIt is legal for anyone at any age to drink, but off-premise sale or supply to anyone under the age of 20 is prohibited and on-premise establishments are prohibited from serving alcohol beverages to anyone under 18. It is legal to serve an underage person alcohol in a private place, provided it's a limited amount and done in moderation.
You can find more legal details and links here:
Wikipedia Legal Drinking Page