"Syntactic sugar" generally means a syntax that's just a nicer-looking version of something that can be equivalently expressed in a more fundamental syntax. But C is more than that: it provides a way of abstracting away the details of the machine so that you don't have to explicitly deal with the fact that your machine has 64-bit pointers and 2's complement integer arithmetic and IEEE floating point and an instruction set that handles shift operations in a particular way.

So a better formulation might be: "C provides an abstraction layer on top of a computer's memory model and instruction set that will allow your code to be portable between different machine architectures, but only if you play strictly by the rules."

By the way, the classic K&R book explains the fundamentals of C pretty well. If you really want to understand C, I'd recommend reading it cover to cover (it's pretty short).