In early 2017, Steve Hanft ripped and put up a short old tape on Youtube. It consisted of some duets he did with Beck, as well as some Liquor Cabinet songs (a band they were both in). The picture of the tape is labeled "Bogusflow" and dated December 1993.
"Smear The Sauce" is a quick blip of a song near the end of the tape. Steve sings most of it, though Beck comes in for the final line... makes me wonder if there's a longer version of it!
Also over on ebay, there's been for sale Beck's first single, "MTV Makes Me Want To Smoke Crack." (It's going for $1200, and been listed for awhile. WAY overpriced.) Anyway, the record has a poem scribbled on it that I guess Beck autographed years ago, which includes the lines "smear the sauce" too.
You can see that here: