I hope you don't mind, I edited your category to reflect criminal defense, rather than juvenile; although this case may involve minors, I assume you are no since you are charged with purchasing alcohol (which implies you are 21+). A sentence for an individual defendant depends on a lot of factors which can't really be determined here (prior criminal history, nature of offense, employment, etc.). While this charge carries the possibility of one year in jail, it's a misdemeanor and other sentencing options are available (like community service, adult offender work program, etc.). Additionally, there are some defenses that you should speak to an attorney about. You should discuss your specific situation with an attorney to find out the likelihood of jail time.
Please don't forget to choose the "best" or most "helpful" answer. This response does not create an attorney client relationship. The information provided here should not be relied upon and is not a substitute for legal advice received by an attorney that you have retained for your specific case. If you are actually involved in a case pending in court and you have an attorney, you should speak to your attorney and follow his/her advice. The information provided here is for general purposes only.