Health science question (wacki?)

[SomethingClever]

I've heard that it takes a few hours of exercise to truly burn fat, because your body will burn its other energy sources first, only using the fat up when they are exhausted.

What if you tried to "cheat" your body by consuming only sugar and then exercising?

Since sugar burns rapidly, would it be possible to enter the fat burning stages more quickly?

Disclaimer: I'm not trying to lose weight. I just have noticed that I become physically exhausted rapidly when I've had too much sugar. It made me wonder what my body was running on (while I was playing basketball), because I had clearly run out of sugar fuel.