If your mat has become more stinky than sticky due to bacteria left by your hands, feet or sweat, I suggest you follow these steps to ensure your mat is clean and odor-free.
Heavily Soiled: Washing machine is not recommended. Your mat may loose stickiness and its shape. Instead, submerge your mat in a solution of warm water and mild detergent (bathtub works well) use very little soap as any residue may cause the mat to become slippery during future use. Thoroughly hand wash the mat and rinse in clean water. After squeezing out the excess water, lay the mat on a dry towel and roll the mat and towel together. Stepping on the rolled up mat will squeeze more moisture out of the mat and into the towel. Then unroll and hang to air dry.”
Lightly Soiled: Use a spray bottle, damp sponge, or terry cloth rag to apply a solution of two cups of water and 
four drops of dish soap. Rub the soiled areas. Wipe the mat with clean water; then rub with a dry terry cloth towel. Hang to air dry.
Yoga Mat Cleaner: 1 part water, 3 parts vinegar, tea tree essential oil. Spray and wipe with clean cloth between regular cleanings. The antiseptic quality of tea tree helps to keep your mat bacteria free.
