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In addition to the obvious firing of striped candies (in singles or combinations) directly through them, all of them will take take one hit from a 2 colour bomb combo. If you can do it when there's no licorice in the adjacent squares, a colour bomb/wrapped candy combo (of an appropriate colour) is very effective.
Do remember though that you don't need to destroy the clock to get the jelly underneath it. It only takes one hit to do that so don't get trapped into wasting shots on them if the jelly's already been gathered. You can beat the level while leaving all of them intact.