Is there such a word as sud referring to just one of many suds?

Suds’s origins are still not absolutely certain. But the American Heritage Dictionary and other contemporary sources agree that a likely source is “Dutch zudse, marsh, from Middle Dutch sudse.” That would mean that suds began life as a singular, and though it could, like kudos, be reinterpreted as plural and sprout a new singular form, it hasn’t done so yet.