I do not remember where I learned this, but I am so glad I did. This tip has always worked for me. The easiest way to remove labels and sticker residue from glass jars is as follows:
Peel the label. (Soaking in hot water helps.)
Rub any sticky areas with peanut butter.
Rinse and enjoy, knowing that no chemicals were needed!
Not only did you avoid spending money on some sort of cleaner, you also got to play with your food!
Removing Labels from Mailing Boxes