The salt water technique works (or at least, worked) because the older machines sent an electric signal through the coins to test magnetic properties (slugs are magnetic, coins are not). This Achilles Heel could be exploited with ANY conductive liquid, not just salt water (bleach comes to mind). Of course, salt water is a bit less corrosive than bleach, which is extremely painful when splashed in the eyes.

The best method for getting this to work is to put at least one coin in while pouring the conductive liquid down the coin slot. Alternatively, you can try flooding the machine with salt water -- but this rarely works and you'll only end up with the tell-tale stream of water mysteriously coming from under the machine.

In my experience, once the machine has short circuited there are three possibilities: first, that the machine will simply die until reset; second, that the machine will give you any amount of soda you want; third, that the machine will give you change. You can tell the machines that will give money if you put in, say, five nickels, then press the coin return and get a quarter.

The harsh reality of the whole situation is that these salt-able machines are a dying breed. I once took a saunter over to MIT in the freezing cold across the damned smoot bridge figuring that MIT would have the largest supply of vending machines in the Boston area. With 2 two-liter bottles I was hoping to fill my sack with Coke and Pepsi, but instead got: one Lipton ass-flavored Tea and one Yellow-flavored Diet Shasta. Needless to say, the hike back across the bridge was not a happy one. YMMV