I believe your referring to "25662"
This charge is a misdemeanor. (Business and Professions Code sections 25662.) The maximum punishment is a $250 fine (but with assessments that can be up as high as $800), OR 24 to 32 hours of community service.
Since it's a misdemeanor, if you cannot afford an attorney, one will be appointed for you and you will need one. Because there is a mandatory one year drivers license suspension. (Vehicle Code section 13202.5.) An attorney can possibly help arrange for a plea to a different charge which will not effect your license. Although with the prior DUI, I wouldn't count on it.
You really need to stop drinking, because having a DUI and alcohol possession charge on your criminal record, before your even 21, is a bad sign and the courts aren't going to take it lightly.
Here's the actual code:
25662. (a) Any person under the age of 21 years who has any
alcoholic beverage in his or her possession on any street or highway
or in any public place or in any place open to the public is guilty
of a misdemeanor and shall be punished by a fine of two hundred fifty
dollars ($250) or the person shall be required to perform not less
than 24 hours or more than 32 hours of community service during hours
when the person is not employed or is not attending school. A second
or subsequent violation shall be punishable as a misdemeanor and the
person shall be fined not more than five hundred dollars ($500), or
required to perform not less than 36 hours or more than 48 hours of
community service during hours when the person is not employed or is
not attending school, or a combination of fine and community service
as the court deems just. It is the intent of the Legislature that the
community service requirements prescribed in this section require
service at an alcohol or drug treatment program or facility or at a
county coroner's office, if available, in the area where the
violation occurred or where the person resides. This section does not
apply to possession by a person under the age of 21 years making a
delivery of an alcoholic beverage in pursuance of the order of his or
her parent, responsible adult relative, or any other adult
designated by the parent or legal guardian, or in pursuance of his or
her employment. That person shall have a complete defense if he or
she was following, in a timely manner, the reasonable instructions of
his or her parent, legal guardian, responsible adult relative, or
adult designee relating to disposition of the alcoholic beverage.