Yup vinegar is a good cleaner, it works better if warm, adds its touch, alcohol by itself is pretty strong and can really clean, salt (not much is needed) helps with more of action, and makes the cleaning faster i guess....
... On the other hand you can just use Drano (j/k don't do it...).

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More info on vinegar :
http://frugalliving.about.com/cs/tips/a/vinclean_3.htm
http://www.angelfire.com/cantina/homemaking/vinegar
greenlemon Reviewed by greenlemon on . Glass Cleaning Recipe This recipe I use to clean the inside of my glasses, so far no scratches, will work the best if you don't let the dirty stuff sit too long before cleaning (I clean my glass with this every other day), the ingredients are easy to obtain, you may have all of them already available. Ingredients: Alcohol - (96 is fine, everclear, pure grain alcohol, the stronger the better). Vinegar - (White, rice, wine works fine, you may squeeze some lime too). Grain Salt - (Sea salt). Rating: 5