If you are speaking about oral herpes that commonly causes cold sores, then the answer is yes, it can very easily be passed through saliva and other secretions. Because of that, it is commonly passed around, and most people come into contact with the virus between the age of 1 and 6 years old. Many people will have no reaction or only a very mild reaction, and will not even know that they have the virus at all. It is quite possible that you are one of those people, and have had the virus for some time without even knowing. Because of that, it is doubtful that you will develop an outbreak of cold sores or the other effects of the virus just by having shared his drink.
That being said, there are other manifestations of the disease as well, and everyone does react differently, so please discuss the issue with your physician if you notice any concerning symptoms. Additionally, sharing cups is an excellent way to share other illnesses and viruses, and, as you obviously know, is asking for trouble. If you do end up with cold sores, either the ointments or pills that are available for the condition are effective at reducing the symptoms. Please talk to your doctor
if you have further questions about treating cold sores.