Keep your pantry well-organized, with oldest products at the front of the shelf to be used first. This will prevent you from opening a can of "out of date" pumpkin puree that has a metallic flavor, or from pulling a rock-hard bag of sugar off the shelf to refill your sugar canister.
However, if your sugar bowl is empty, and your sugar canister is also empty, and if you really need that sugar for your coffee, and the bag of sugar you found to refill them all is hard as a rock ... a potato masher can break up the chunks of sugar-rocks. Just pour the bag of chunks into your canister, then mash away. A twisting action helps to break them up faster. Press, and twist. I suspect this will need to be done again, once you've used the top layer of sugar and more chunks are exposed.
Of course, my OWN pantry is perfectly organized and I would NOT have any experience with rock-hard bags of sugar. Not at all. Ahem. Moving on.
(shuffling feet and glancing around nervously as she tosses the potato masher into the sink)
Just don't look in my sugar canister, please.