DIY Garden Bug Spray If you have an issue with bugs eating your plants in the garden, here is a DIY Garden Bug Spray you can try to get rid of the pests. Put 2 cups of onion skins in a container. Add 4 cups of boiling water. Cover and let soak for about 3-4 days. Then remove the onion skins and pour water into a spray bottle. Shake well and spray both sides of the plant leaves.