Since we use oil-soluble glue for the labels, the best way to remove the label from the coconut jars is with oil. Simply coat the label with oil, let it absorb overnight and peel off easily in the morning. However, if the label is already off and only the glue is on it, this method doesn't work as well. In this context, we have been told of positive experiences with orange oil cleaner, such as from AlmaWin or Sodasan. Another option is a hair dryer - because heat also loosens the label well. 
Get more suggestions at Upcycling & Creative.