This article gives two examples where UB arguably helps you, and in each case the article itself mentions a cleaner and better way of doing it.

Magic behavior of "int" (but not "unsigned int") --> just use a type that's the correct size and better conveys your intention, like "size_t".

(And that one doesn't make your code "many times faster", in the example given it saves a single instruction.)

Type-based assumptions about aliasing (with a special case for char*) --> be explicit about your intention with the "restrict" keyword.