If you water plants with coffee it can make the soil too acidic although the coffee that is diluted can provide the plant with nitrogen, potassium and magnesium which can benefit plant growth.
But used coffee grounds are better for the plants instead of watering the plant with coffee.
Diluted coffee though is a good fertilizer for many plants.
The diluted coffee or even coffee grounds raises the soils acidity which are beneficial for many plants but not all.
Eggshells are good for plants and can benefit the plants health.
When eggshells are crushed up and placed in the plants soil, the eggshells work as natural fertilizer for the plants and provides the plant with calcium which is important for plant health as well as the proper development of cell walls.
Eggshells can also improve the plants soil structure and nutrient content.
Eggshells also deter slugs from the plants as well.
Eggshells also can help balance the soil, pH, making the soil less acidic, which can also benefit certain plants and calcium in the crushed eggshells also makes the plants more resistant to disease and pests.
Plants also need the calcium from eggshells for healthy growth and development.
However a common myth is to use sugar water on plants but sugar water should never be used on plants.
Sugar water is not good for plants and can actually be harmful to plants.
Some garden myths state that the sugar water can help the plant with plant shock or provide extra nutrients.
However scientific evidence and practical experience indicate that the sugar water can be harmful to the plants instead.
The sugar water can also interfere with the plant's ability to absorb water and promote the growth of harmful microorganisms and even lower the soils fertility.
For plants to thrive and grow the plant needs plain water, air and sunlight.
Coffee grounds can be beneficial for some plants but can harm others.
Plants also do not digest the sugar like humans and the plants already produce enough of their own natural sugar through photosynthesis for their needs.
Sugar water can also attract pests and other insects and lead to infestations which can further harm the plant.
Chemical free water is the best for plants such as rain water or well water without any chlorine.