For the conditions of the contest as described by the OP, I would think sugar water would work the best. Most food won’t pass out of the stomach until it is digested, while water doesn’t have to be digested at all - the body simply absorbs it. At the point where one’s stomach is completely full, the less time the food spends in the stomach the sooner one can consume more. If you knew about the contest in advance you could prepare by sitting in a sauna for a few hours beforehand - it’s amazing how quickly the body can absorb water when it’s dehydrated.
Going by this here chart, it looks like your best choices are molasses or corn syrup, with honey being right up there. The figures seem to be around 11.5 to 12 ounces per cup for those, versus 8 ounces per cup for water and 4 ounces per cup for sugar. So, for the same volume-weight of corn syrup, you’d need a cup of water AND a cup of sugar, perfectly dissolved together (and wouldn’t that much sugar over-saturate the water?), so you’d lose available volume.
Speed of consumption is going to be a real factor with thick sticky liquids, though…
In order to win the contest I’d think you’d want to store as much weight as possible in your digestive system / body. Water is good since a lot of it is abosbed into the body. The remainder will digest very quickly and fill your bladder with weight. You’d probably have to find something that digests quickly with some substance to fill your large intestines as quicly as possible. Maybe some bran and prune juice.
I think the key would be to get completely hydrated, have a full bladder, have full intestines, and a full stomach.
Pumpernickel. Not the bread served in the States, that, while heavy, is still created with milled flour and yeast that has been allowed to rise, but the pressed seed loaf that I encountered in Belgium, where a 455 g loaf is about 10 cm on a side.
Wheat Snack Bread.
Well yeah, that amount of sugar will produce a saturated sugar solution. That is exactly what molasses and corn syrup are: saturated sugar solutions. And no, you wouldn’t lose any volume at all.
This was precisely my point above. Crystalline sugar, as you have discovered, is light because it contains a lot of air. You need to exclude that air with the bare minimum volume of water. The aim isn’t to dissolve the sugar, simply to fill the air spaces.
Since sugar itself is much denser than water you ideally wouldn’t add any water at all, but you are forced to in order to exclude the air. So you add the bare minimum water and end up with a saturated sugar solution such as syrup, honey or cornstarch.
Hard candy should be even better because it has had almost all of the water extracted by heating, leaving what is essentially one gigantic, solid sugar crystal. However I’m not sure how the density of crystalline sugar stacks up against a strong sugar solution. Sucrose and glucose behave in a funny manner as they transition from a linear solute to a cyclic crystal. If hard candy isn’t denser then a sugar solution then taffy would presumably be the densest possible form.
There are density data for a number of substances here. Of the digestible items on that list, it looks like sucrose wins at 1.58 g/cm3.
For indigestible but nontoxic solutions: barium sulfate oral contrast solution, density of 2-2.5+ g/cm3, pdf here. You could push the density up toward 4.5 g/cm3 if you don’t mind it getting pasty and solidifying in your gut as the water is absorbed.
If there’s too much sugar or salt in the solution, you’ll hurl.
Not even close. The same volume of pure water is 1000 grams, saltwater somewhat more, and there are plenty of foods denser than saltwater, as brossa points out.
And do they actually sell bread in 455 gram loaves? This metrification thing is going slower than I thought.
You think that’s bad? I saw a damage report recently that described some damage as being “25.40mm wide by 50.80mm long” [no. of decimal places in original]
I was going to make a crack about the densest food ever being a loaf of homemade sourdough I made once. It was so sour I literally could not eat it except in nibbles with big bites of soup, yet it never rose. Weighed a couple pounds. No crumb. Yech.