It is just a matter of word order. In English, there is a more logical word order but we can sometimes change the word order to emphasise (stress, highlight) a particular thing.
We usually put hardly in mid position, between the subject and the main verb "He hardly had any strength left" but it would not be incorrect to do it your way: He had hardly any strength left - it is just a little less "usual" :) Sometimes the word order is not flexible and changing it would result in an incorrect sentence - but not in this case.
I hope it helps.
Good luck with your FCE preparation! :)