The simplest cleaner of all is probably water. Water is a universal solvent and can effectively clean many surfaces and materials. It's safe, easily accessible, and doesn't leave behind any harmful residues or chemical odors. For everyday cleaning tasks, water alone can be quite effective in removing dirt, dust, and some stains.
Of course, for more challenging cleaning tasks or specific types of dirt and stains, you might need to use specialized cleaners. But in terms of simplicity and versatility, water is the go-to option for basic cleaning needs.