Thanks for playing along, everyone.
greatofdeath, looks like you were the closest to guessing it. :)
What it actually is, is ... WAX. Melted wax. (I'd say that qualifies as "baked on.")
Someone placed a huge candle on this defunct vending machine by the dock, and I noticed it yesterday. The blistering Miami sun has turned it into a mess of goo.
Tada! And, incidentally, it smells delicious. Kinda fruity.