There is no single food that can kill rats instantly. However, there are some foods that can become fatal to them when eaten in large quantities. These include chocolate, avocados, and peanuts. It is important to note that using poison to kill rats can be dangerous to humans and other animals, and it is best to use alternative methods such as trapping or natural repellents. Some homemade solutions to kill rats include:

• Peppermint: Rats have a very distinct sense of smell, and peppermint is offensive to them. To use this method, add 25-30 drops of peppermint essential oil to a cotton ball and place it in areas where rats are commonly found.

• Mothballs: Mothballs can be bought from department stores and placed in areas where rats can be found.

• Ammonia: Ammonia is known as a cleaning agent, but it also acts as a poison to mice and rats. To use this method, mix 2-2.5 cups of ammonia, 100-200 mL of water, and 2-3 spoonfuls of detergent in a bowl and place it in areas where rats are usually seen.

• Onions: The smell of onions is very offensive to mice and rats and can lead to their death. To use this method, slice onions and place them where mice and rats are commonly found.

• Instant mashed potatoes: This method involves placing bowls of instant mashed potatoes in the rats path. The rats will eat the potato flakes, and the baking soda mixed in with it will kill them.

It is important to keep in mind that homemade solutions may not be as effective as professional pest control methods, and it is best to consult with a pest control expert if the rat infestation is severe.