A method of eliminating microbes in an overflow space in a sink having a sink basin may include obtaining a liquid dispensing and effluent shielding container assembly including a splash guard including a splash guard shield and an injection nozzle carried by the splash guard shield, the injection nozzle having an injection nozzle bore and at least one injection opening in the injection nozzle, the at least one injection opening, disposed in fluid communication with the injection nozzle bore; inserting the injection nozzle of the liquid dispensing and effluent shielding container assembly in the at least one overflow opening in the sink basin until the splash guard substantially covers the at least one overflow opening; and expelling the antimicrobial or cleaning agent liquid through the injection nozzle and the at least one injection opening and into the overflow space in the sink basin of the sink, respectively.