Why Do Burgers And French Fries Taste So Much Better With A Soda And/Or Milkshake?

There's actually a little science behind this. Our tastebuds have evolved to enjoy the tastes of sugar, fat and salt, especially in combination. Your standard burger and fries have plenty of fat and a good dose of salt, but even the fries that have had a touch of seasonally-adjusted sugar added by major fry-makers don't have any effective sugar in the flavor profile. Your standard milkshake has plenty of sugar, and lots of sodas do as well. This is also why some people like ketchup and pickles on their burgers, because they do add some sweetness along with the zing.

Incidentally, this is also why KFC fried chicken tastes so good. As near as my tongue has been able to tell, one of their secret ingredients in their spicing is sugar. That goes along with salt and the fat from the deep-fry. To be fair, as near as my tongue can tell they only use the minimum amount of sugar to invoke the trinity of sugar, salt and fat--they don't go overboard. I respect that.

There are 5 different sensations ofTaste: sweet, salty, sour, bitter, and savory (also called umami). Generally speaking, sweet comes from sugar, salty from rock salt, sour from acidity, bitter from alkalinity, and savory from proteins, especially those rich in glutamate. Temperature also contributes as does texture, though the latter is poorly characterized.

Burgers
The meat in the burger issavoryand I'm betting you use sauces like ketchup. As many sauces are made from tomatos or pickled cucumbers, it's a safe bet that they're slightly acidic, which tastessour. And the burger will be relativelyhot.

French Fries
Obviously, the fries taste verysalty. The frying process also causesCaramelizationof the potato sugars, indicated by the yellow/light brown color. This results in a slight sweetness, which actually enhances the saltiness even more, rather than cancelling it out. The fries are probably alsohot.

Milkshake/Soda
This is obviously where thesweetnessdominates. And unlike the burger or fries, the milkshake is relativelycold. I predict texture also plays a role since milkshakes have uniform consistency compared to a burger or fries. The same is mostly true of soda, except soda tends to be very acidic. Not sure how much this affects the taste.

TheFlavorof food is the combination of taste, texture, and temperature - the more of these you hit, the better it 'tastes' - and the only one missing isbitter.