Drooble's Best Blowing Gum is sold at Honeydukes in Hogsmeade and on the Hogwarts Express Food Trolley for two sickles. It is a brand of chewing gum that allows the consumer to blow bluebell-coloured bubbles which will not pop for days.
Behind the scenes
Real world version of Drooble's Best Blowing Gum
The Hasbro Company sells a cotton candy-flavored version of this candy that makes the inside of a person's mouth turn blue.[1]