From the OP's site, here's a good one:
http://pundo3000.com/htms/7.htm

Oh dear... no amount of advertising can make this look good:
http://pundo3000.com/htms/12.htm

A lot of these are foreign products, so I don't know what the rules are, but I believe in the US, as long as everything shown is actually in the product, it can be arranged any way they want. So, taking that rice ball example that Morrigoon just posted, as long as the amount of carrots, peas, and spices (I think that's what all of that is) is somewhere in the actual ball of rice, it's perfectly allowed. It doesn't matter that in the picture they just all happened to be located around the outside instead of evenly spread through the whole thing as they are in reality.

Years ago, we studied such things in a media class. Back then, photoshopping wasn't an option (although airbrushing was) and the photogs had to get real creative. Vaseline on the lens, plastic ice cubes, Elmer's glue instead of milk, and so on. It was a fun class, and I've never looked at advertising the same since- especially food ads.

Elmers?! Really?! The irony!

Milk shows up another color (I want to say yellow or green, but it may be blue), so glue is used as a substitute.

Plus the hot studio lights tend to make food go bad quickly.

My understanding is that the law regarding food photography in advertising is that the actual item being sold must be real in the photographs (of course, that doesn't mean you can't do just about anything you can think of to make it look better) but that surrounding items can be fake.

So, if you're selling cereal you can use fake milk but not cereal in the photo. But if you were selling milk you could use fake cereal but not milk in the photo. And you can have 45 toothpicks inside the hamburger you're photographing to keep it perfectly formed and perky.

But that is coming from dim recesses of my brain so I may be misremembering or have learned untruths.

For this reason, I've heard that mashed potatoes are used in lieu of ice cream.

On a movie set, that's often been the case. But for close-up photography, it would be very difficult to get smashed taters to look like ice cream.