Food flavourings can really be obnoxious things to try and get out of
plastic.  The smaller pails from bakeries with pie fillings, etc. are hard
to clean but certainly not impossible.  TIME is as important as elbow
grease.  If the bakery steams them out before they store them, and then you
soak them in cleaner of your choice for a good time and then leave them air
for a good time and finally clean them again just before filling, I don't
find any residual odor.
 
We have a large supply of good quality five gallon pails used here for
beverage flavouring at the local pop plant.  It takes a good year of use for
other purposes  (feeding grain, or milk replacer, etc.) before you can scour
them and really get rid of the last traces of that flavouring.  By that time
they may have picked up some other strong odors :)
 
But one of the easiest five gallon pails to clean is the one used by the
fast food restaurants for their frying oil concoction.  It has practically
no odour, and it cleans off easily with detergent and water.  The
disadvantage is the lid.  The pail is of the same type as those used by
petroleum products companies and has a spout and locks that you must cut and
an o ring seal. Not nearly as nice as a snap lid.  But if you cut the locks
carefully, and don't cut the o ring, the lids will keep the honey airtight.
You have to take the o ring out to clean the lid well.
 
There is something to be said for new buckets.  At present honey prices,
$4.00 is only  about 6 percent of the value.  With small packages the
containers can be 25% sometimes.