Traditionally I used lemon juice and water- but as I soon discovered as I read up on natural rubber mats (which mine is), they are mostly what is known as "open celled" mats. This means that their cells are open and absorb stuff... like lemon juice and... well ... sweat. My mat acting as a sweat sponge really made me want to clean with something that might help with bacteria growth. Which led me to the "Abominable Fingers" episode which was very traumatic. I guess I'm allergic to tea tree oil.
The result of swollen fingers and rash-face (where I wiped the sweat during practice) was that I had to dump my mat in the bathtub and make sure ALL the tea tree oil was completely eradicated. I thought I would just revert back to my lemon juice attempts.... but no- my mat hates me.
I never truly considered why open-celled rubber mats would be more sticky than closed cell PVC or TPE (thermoplastic Elastomers- not really a fantastic eco-solution) until the bathtub cleansing dunk. Ever notice how your rubber mat needs to be "broken in" for a bit before it will really start to get sticky? My theory is it's the mat slowly adjusting to your sweat (of course, I am no rubber-mat sweat scientist). With open-celled mats, sweat that would normally be between your hands and feet causing slippery-ness is absorbed into the mat. Instant stick.
Unfortunately for me, this meant that when I dunked my mat to clean off the tea tree oil AND to wash off the oodles of sweat from my hot yoga experience my mat had no more sweat absorption ratio. It was filled with water (even though I squeezed, patted and twisted all I could out of it). This meant that for on average about a week after I washed my mat (and witnessed the stink of the water that was transformed into a muddy brown... my sweat is so pretty!) I could barely perform downward dog without falling on my face. On average- three yoga practices before I even started to feel like my mat was normal again.
So now I'm afraid to wash my mat. I will probably just continue to wipe it down with a cloth, some lemon juice and a TINY bit of water... but no more tub baptisms for my green Lotus Wear Mat. I know some people who put their mats in the washing machine, but I have to pay for my wash and besides, one load for one wash is wasteful.
For another viewpoint on eco-mats check out Om Shanti's blog here. :)