Mint Extract: If you favor neither the smell of citrus nor vanilla, you can perhaps use mint extract instead. Pour several drops of mint extract on a couple of cotton wools. Toss the cotton wools inside the confined space and leave them for a couple of days.
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.