Since garlic is powerful antiviral and COVID 19 is respiratory tract disease, do you think vaping garlic would kill the bug?

That could certainly reduce close meetings between people.  

I doubt it.  They say garlic repels vampires.  However, the local phlebotomist thinks my garlic necklace is cute (as she sucks out 3 vials).

There is a product callef Allicin, which is a proprietary name for stabilised garlic extract. It is marketed for its immune-strengthening properties. It says in the enclosed instruction leaflet that eating raw or cooked garlic won't have the same effect because the active ingredient is broken down in the stomach. I can't confirm or deny this as I don't know what tests have been done.

All members of the onion family help to feed good gut bacteria along with green veggies and some other foods.
When the gut biome is healthy, this has a major effect in improving overall immunity.

Other immune boosters are plenty of good sleep, moderate exercise in fresh air, and avoiding too much stress.

A good immune system will help us fight an infection and not die from it - but it doesn't prevent us from catching one that the body has never before encountered.

So social distancing and good hand hygiene are the best protectors at the moment.