5. Watering
Water plants with surplus water. For example, if you have half a teapot of tea left over, your plants will thrive on it. If you have some reasonable clean water from washing the floor, then toss it on your garden plants, assuming you don’t have too much detergent in it. Maybe you have a jug of water left over from a meal - your houseplants may be pleased to get it. Maybe you can collect rainwater. You may go much further and install a grey water recycling system, or even a black water recycling system.
If you just pour out excess tea on one plant, the cost and savings are not that great, but if everyone saves water in this way, it begins to add up.
Put a leaf on the tree if you have found a new way to recycle water for plants either in your house or in your garden.