Hello from JustAnswer.
In someone that has not been drinking or using recreational drugs, transient symptoms that appear to be intoxication is usually due to a change in blood chemistry that serves the brain. The most common are from profound hypoglycemia (low blood sugar) or hypoxia (low blood oxygen), although other metabolic conditions can also be present.
Ultimately, he needs to have a proper evaluation to determine the cause of the symptoms. If someone in the family or a friend has a home glucose monitor, you can check his blood sugar level when he is having symptoms, but most of the evaluation would need to be done by his doctor.