I had this experience many years ago....passed out on the New York City subway....NOT fun..luckily I was with a friend. I also do not like salt and do not use it. I went to a doctor....was told to eat potato chips every day....the only salty food I liked. He also told me to eat small amounts thru the day to keep the blood sugar levels more balanced. I kept a few nuts or raisins in my purse, so if I felt like I was getting weak, just eat them and felt better.
Here's a link to foods that raise blood pressure naturally. If you google #8 Tyramine you will get a list of foods that it's in (some cheeses, bananas, pineapple, eggplant, etc) The article is written from the standpoint of what NOT to eat if you have high blood pressure, so you will be looking at it as what you SHOULD eat to raise your blood pressure.
Top 10 Foods That Raise Your Blood Pressure