The standard DUI probation terms generally do not include a prohibition against having a passenger with an open container. But check your probation order carefully.
Generally, violate no same or similar (DUI) law means you should not be arrested for DUI and often you are further ordered to not drive with a meaurable amount of alcohol in your system.
These types of terms would mean you need not worry. It appears you were not cited with anything including any probation violation. Nonetheless, be safe.
If you were the passenger with an open alcohol container, and if you have probation conditions which make it a violation for you to possess or consume alcohol, then yes, this could be a violation of probation. It may also be a violation of probation to fail to report any police contact within a specified period of time.
So -- first, report the police contact to your probation officer. Second, talk to some attorneys to see if you can reasonably fight the ticket.
DISCLAIMER: I do not practice in CA. This answer to a short question is provided solely for general informational purposes and based on general legal principles and court practice. The laws and practices may differ where you are. This answer does NOT constitute legal advice, create an attorney-client relationship, or constitute attorney advertising.