If you have a potent stench coming from your sink, it could be your poor, abused sponge. You can keep two of them around and rotate use so your sponges won't develop a mildew smell ever again.
The Reactions channel on YouTube took a look at the chemistry behind a smelly sponge. Reactions explains that constant moisture is what's letting the sponge stink up the place. It's important you thoroughly rinse a sponge after each use and let it dry before each use, otherwise bacteria take residence and release odorous chemicals.
Two sponges -- one for the first half of the day, the other for the second half -- will ensure that your sponges will have ample time to dry out. If one of your sponges is smelly already, you can revive it with some bicarb soda.
Awesome Chemistry Life Hacks (Vol. 3) [YouTube]