I would suggest using detergent first, rinse, white vinegar next, rinse, and then sodium bicarbonate with several final rinses, unless the manufacturer says not to. An acidic soak followed by an alkaline soak should pretty well cover all of the bases. When I sanitize my plasticware, I normally put a little dishwasher detergent gel in it and then fill with water. I let it soak for an hour or so, rinse with water and then wash with dishwashing detergent to get the dishwasher detergent out, then rinse and dry. Dishwasher detergent contains sodium carbonate and bleach and normally does a great job of removing coffee stains and other stuff. It is difficult for me to believe that commercial plasticware would consistently impart a bad taste without some outside factor.