While I understand your wanting normal food to make it fun... Bagels and similar are going to take up a LOT more room than you think in a bear can.
One gallon is 231 cubic inches. Observe (I threw in can weights so you can compare the weight and the volume)
Garcia 2 lb 12 oz 614 cu in
Bare Boxer 1 lb 13.6 oz 275 cu in
BearVault BV500 2 lb 9 oz 700 cu in
Bearikade Weekender 1 lb 15 oz 650 cu in
Bearikade Expedition 2 lb 5 oz 900 cu in
Get a gallon can or plastic container. See how many of your meals will fit in one. Get seven of them (simulate two Weekenders and a Bare Boxer) and see if all your meals for four days and your toiletries will fit in. It won't matter that the container is square or round; your food will be jammed into the space regardless of the shape of the canisters. Heck, a five gallon bucket or one of those cat litter boxes would give you a pretty good idea of what it's like.
If you're going to be taking anything other than food that squishes, compacts and is able to be mashed into small spaces without concern, you will need larger or more canisters. Food that pours or molds without deforming works very well - m&ms, gorp, couscous and powdered stuff is popular for that reason. Sharp sided stuff like pasta needs thicker packaging so it doesn't poke through and tear the plastic. I typically take bulky food to eat the first day - that's when the potato wrapped in foil goes in the fire, or the bagel and cream cheese get eaten for lunch. It won't ever have to see the inside of the canister. For small items I don't want squished (condiment packets, for example) I'll put a small ziploc container in near the top of the canister where the bulk of the food won't be pressing down on it.
I'm not saying you shouldn't take real food if you want it - just that bear cans are smaller than they look. With practice you can get more in. I've hauled a platypus of wine in the top of mine for a few days. (Of course, it got progressively lighter ...
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