Here is a quote from the document I read that suggested strawberries:

Scents I have been successful with include:
-different plants and fruits (flowers, leaves, strawberries, grapes, etc)
-a PINCH of rat bedding
-other snake’s sheds and bedding
-things with my smell on them
Pretty much any object is going to have a smell. It’s hard to go wrong unless you place something toxic in there.
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Link: http://www.natureboxpetemporium.com/...aptive-snakes/