Can you use onion garlic or lemon to kill the smell of alcohol on your breath?

No. Consuming pungent-smelling foods, such as garlic, onions, or lemons, unfortunately will do little to mask the smell of alcohol on your breath.

Alcohol is metabolised in the liver and excreted through the lungs, so masking the odour requires intervention at different stages of digestion rather than simply overpowering it with other scents.