I think the main reason why putting mason jars down would keep the critters away is that it would just be something new that would make them skittish. Once they have been there for a while they will probably loose their effect. I have never heard of particular one, but that is how most ole wives tales got started I believe.
"The hot
pepper, garlic, hair, urines, blood meal etc don't really work." All of these were new scents to the critters at some point. So that is why they may have worked for a while. Some of them such as urine have no real basis at all, and just makes me wonder how the tale even got started. Even commercial scent repellents need to be changed up every so often to keep the critters on their toes and at bay. The best things that you can use are things that carry a strong scent. Those little bars of soap we are all guilty of stealing from hotels, perfume soaked rags, mothballs, human or animal hair, will all work for a short period of time.
Taste repellents are a bit of a different story. The use of hot
pepper on a plant will work if the
pepper stays there. Unfortunately most of the time wind or watering wash it off. There are commercial taste repellents on the market which will adhere to the plant. (they usually have a latex base) This makes them much more effective, but you can't use them on veggies once they start producing fruit, or you will suffer the taste of the products as well.
You say that fences are not an option in your situation. If that is the case, what about some of that black nylon bird netting. This may help to keep the little furry critters away. It is light weight and easy to put over the plants.