I've been using a starter for some years now and have always been under
the impression that a teaspoon of sugar was sufficient to feed it after
a period of non-use. When replenishing the starter, I've always used
water, flour and sugar.

After a long period of non-use and neglect, I found my starter in poor
shape, came here and found the FAQs. I've used the instructions there
to proof my starter, and it seems to be healthy again.

Is there any situation that would call for using sugar to feed or
replenish a starter? I'm not sure where I got the recipe that I've
used, and the starter stayed usable for my purposes although it did
often get a layer of "hooch" after periods of neglect in the
refrigerator.