Taking that a little further,

  const char *fb[][2] = {{"%d\n", "Fizz\n"}, {"Buzz\n", "FizzBuzz\n"}};
  int i;
  for (i = 1; i <= 100; ++i)
          printf(fb[i % 5 == 0][i % 3 == 0], i);

(It's a pity we have to specify the second dimension manually . . .)