Green’s Dictionary of Slang

(US tramp) something sweet, esp. old cakes.

1929		V.W. Saul ‘Vocab. of Bums’ in AS IV:5: toppings: dessert.
1936		K. Mackenzie Living Rough 236: ‘Got any toppings (old cakes and cookies)?’ I asked the lady behind the counter.
1944		O. Ferguson ‘Vocabulary for Lakes, [etc.]’ AS XIX:2 103: When they were young on the road someone threw them into awful confusion with the question, ‘Are you a topping bum or do you bum lumps?’ (Toppings are dessert, or any bakery stuff).
1950		Goldin et al. DAUL 224/2: Toppin’s. (Hobo: far West; California prisons) Cake with icing, sugar-top, etc.
1991		O.D. Brooks Legs 2: All we got is a sack of toppin’s and dry bread.