An explanation to why cats, unlike humans and other mammals, are indifferent to sweet flavors was answered by a video report from the American Chemical Society.

At the Philadelphia Zoo, he gave lions, tigers, cheetahs and housecats two different types of water - sugar water and regular water. The cats showed no preference to the sugar water, suggesting a physiological difference between other mammals, such as humans, monkeys and dogs.
The video explains how scientists from the Monell Chemical Senses Center later uncovered the cause behind the cat's missing sweet tooth.
In place of a functional sweet taste receptor gene, they discovered that cats have a pseudogene, or a broken gene, that makes them unable to detect sweet tastes.
Source-ANI