Pour 2 tbsp. of ground coffee into a coffee mug. Add 1/2 cup of water.
Place the mug in a small microwavable bowl and sit it in the microwave. Heat the coffee on high for two minutes.
Remove the bowl and mug from the microwave. The coffee should have absorbed the odors and eliminated the smell.
Fill a large microwavable bowl with 1 cup of water if the smell persists. Add 20 to 30 drops of lemon or vanilla extract. Place it in the microwave and heat it on high for about two to three minutes to bring the water to a boil. Let it cool off in the microwave for 15 minutes, remove it carefully and wipe down the walls of the microwave with a rag.