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.
Pandan Leaf: It is easy to get pandan leaf in tropical countries as it is widely used in Southeast Asian cooking to add aroma to dishes. Its pleasant aroma also acts as natural air freshener. Just take a few strips of the pandan leaves and tie them into knots. Place the leaves inside the confined space and leave them until the leaves are withered or dried up. Replace the leaves regularly until the trash can smell goes away.