Bereishis Rabah 28:7: The money that Yisrael took out of Egypt was a pitfall for them.

Rashi: They made copper coins and covered them with silver to swindle people.

Maharsha (Bava Basra 15b): A buyer would make the dross on his silver coin look like silver [so the seller would think that it is clean silver].

Rashi (from Pesikta d'Rav Kahana): Their drinks are mixed with water (Radak - the buyer thinks that it is pure wine ¹ . Sav'ech is wine sold in a store. It is called so, for empty, frivolous drunkards come and get drunk ² there). We do not find elsewhere that "Mahul" means mixed. A Midrash explains that "li'Schok Amarti Mehulal" (Koheles 2:2) means mixed. Radak citing his father - in Arabic, Almahal means mixed. Malbim - this answers how they descended to such a level. It was not sudden. Even before, people gave silver with dross, and even before that, they mixed water into the wine.