When my family member was manic, he neither ate nor drank, but would drink water if a cup was held to his lips. I was the other person from whom he would receive food or drink (paranoid of all others).
Also, he started eating plants during the time he was missing, including oleander. Had to have charcoal at the hospital (he had very little in his stomach).
What's strange about Erin's situation, though, is that she had had a normal enough day on Monday, apparently lunching with a friend. Most manic people would not sleep much, and if the car was out of gas, would then be out and about on foot, manic. Manic people don't sit still much (although there are mixed states in which they are stuporous mixed with manic walk-abouts).
We’d need some medical expert to chime in, but does that explain the apparent manic behavior being exhibited here?
This seems to have been a fairly prolonged event, one in which she was driving around and making phone calls.
Thats the reason I’m leaning towards some sort of drug, but I’m not a doctor.
I worked as a field diagnostician for jails, mental hospitals (and in other settings) for a couple of decades (and I am a doctor, just not an M.D., a biological anthropologist). Mania can go on for a week or 10 days. Its close cousin (hypomania) can go on for months, to the point that most people regard that state as the person's "normal" state.
I actually worked in Palo Alto, Menlo Park and Mountain View for some of those years. Lots of bipolar/manic behavior in that area (there's an excellent book on bipolar illness and its relationship to creativity and innovation by Kay Jamison, who is herself bipolar).
When people showed up in the ER where I was working and were "manic" or "psychotic," it was very hard for anyone to tell whether it was drug-induced (always among the first questions asked and in the bloodwork that gets run ASAP). When people are floridly psychotic, it's hard to distinguish manic, drug-induced, schizophrenic and other psychoses. Typically, first line of treatment is an anti-psychotic drug, naturally. Then as the psychosis subsides (or is knocked down, in some cases), the psychiatrists and other carers can start pinpointing what type of illness it is, with a view toward longterm treatment.
Some forms of mania seem to be related to seizure disorders, for example.
Bipolar disorder in neurologic illness
There's also a phenomenon known as "kindling," in which the psychosis is brought on by a related mental state (excitement, drug use, sleep deprivation). It was not uncommon for people to come into our hospital while on a visit to the area, since travel can induce either bipolar mania or, in type II bipolars, depression. Medical treatment is different for each and kindling situations are something the sufferer must learn to deal with/avoid.
All that being said, anti-seizure medication is increasingly used in the treatment of bipolar illness, and there's some research to indicate that seizures can bring on what appear to be manic episodes.
Thirty Years of Clinical Experience with Carbamazepine in the Treatment of Bipolar Illness
I know several psychiatrists who have had to deal with mania in patients who were at a distance from treatment (traveling) and they advised something as similar as benadryl during a hypomanic or manic episode, as a readily available "bridge" treatment until the person could get to an ER. Most manic people will not, however, go to an ER. They are usually brought in by police, after concerned citizens notice their strange behavior.
Just this week, while at a local business, an apparently manic homeless person came to the door and began shouting exhortations at everyone there, all women and children. He was bare footed and bare chested, wearing nothing but very loose shorts.
Everyone moved to the back of the place, in fear, instantly (except me and the owner - I'm older and I've worked a lot with homeless people). Since he was barely clothed, it was pretty easy to tell he was unarmed and his hands were visible (he was waving them all around and touching things in the front of the store, all the while shouting). I had my phone out to call 911 but just as I started to dial, two squad cars pulled up (he had been wandering all around the shopping center, people had called in). That is an example of florid psychosis. This man was made to sit down on the ground by the police (which helped calm him but he kept shouting for the next half an hour, until they got ready to transport him, 5150).
Sometimes, the more a manic person is allowed to pace around, run around, be hyperactive, the more manic they become. Erin was not, as far as we know, all the way to disrobing and trying to enter houses that were not her own. Which is why it's very puzzling. Sure, she could have been confused and manic, but why did she stay in her car?
Only the medical examiner can answer the question of how long she's been deceased, and whether the toxicology report shows any *known* drug. There's always been a market for strange and experimental drugs in and around Stanford (and people who know how to make them), and there's been a resurgence in the use of synthetic psychedelics in California (especially in the Bay Area).
I feel so badly for her husband and parents. Mania can come on very quickly. We don't know if she had a previous history of such episodes (her husband describing her behavior as "manic" may be a clue). The fact that she wasn't outside the car, wandering around and eagerly trying to get things done/talk to people makes me wonder a lot about what was actually going on.
The thing that bothers me is you've got an officer admitting someone not from the area making no sense. 
