Let’s say you have prepared onion paste in the mixer jar and now it is smelling like anything. To remove the bad smell, you need to first wash it thoroughly. Once done, you need to wash it again, but this time you need to add some grinded lemons in it. Also, add some baking soda in it and let it sit for 5 minutes. After that wash off the jar thoroughly. This should remove the annoying smell from the jar.