Something growing in mulch
From the picture you provided, I believe what you have is Elegant stinkhorn (Mutinus elegans), sometimes called Dog's stinkhorn, a harmless fungus that emits a foul odor.
Elegant stinkhorn forms 4- to 7-inch long fruits, typically less than an inch thick. The spongy stalk is usually a light pink toward the base and a deeper pinkish-red toward the tip. A slimy brown spore mass coats the top third of the stalk, giving it the unpleasant odor. This fetid slime attracts flies and other insects that pick up the spores on their bodies and disperse them.
Elegant stinkhorn usually grows in small groups on the surface of mulch, wood chips or decaying plant debris during periods of mild and damp weather. They're most commonly found in mulches and composts that tend to retain moisture and stimulate microorganism activity, including that of many bacterias and fungi.
While Elegant stinkhorn is harmless to your garden, the foul odor makes it a nuisance. Since stinkhorns are most commonly found on mulches and composts with a high hardwood bark and wood chip content, making the switch to pine bark mulch or pine straw could help deter stinkhorn formation. Alternately, adding grass clippings to your wood waste before composting it reduces the carbon to nitrogen ratio in your compost to help deter stinkhorn growth.