I once heard a story that the Brisker Rav was seen drinking water outside the Sukkah. His talmidim asked him why he is not machmir to drink only in the Sukkah like the halacha says, after all, he kept many other “chumras”. The Rav answered that he does not keep chumros, rather, what everyone sees as chumras are actually sfeikos in which he is machmir. By drinking in the Sukka, the halacha specifically says that it is only an extra hiddur and is not in any way a safeik.