I would guess that popcorn would be the worst - those corn husks are definitely insoluble fiber that would come out as scratchy as it comes in.
Candy should completely dissolve - it is pure sugar - it dissolves in a cup of a tea in couple of seconds, not to mention in 12 to 24 hours in digestive juices
I think that one should worry only about big particles of insoluble fiber - husks, particles of shells , nuts, pits, tiny seeds that are not chewed (grape, accidental tangerine seed etc. ) and corn products that are made of coarsely
milled DRY corn - that is very hard to digest, if at all ! Cooked corn is ,of course, safe.