Lemon or Lime Peels: Just put some lemon or lime peels into an uncovered container and leave them inside the confined area for a couple of days. The citrus smell will naturally replace the bad trash can smell.
Coffee: Ground coffee has a nice, crisp natural aroma. Just put about a cup of ground coffee in a flat, uncovered container. Place the container inside the confined space for several days. If the bad smell is extremely horrible, put more ground coffee. The area will smell of fresh coffee for many days.