Green’s Dictionary of Slang

tears of the tankard n.

drops of liquor that fall onto the careless drinker’s clothing.

[UK]B.E. Dict. Canting Crew n.p.: Tears of the Tankard Drops of the good Liquor that fall beside.
[UK]Penkethman’s Jests 85: An idle Fellow, who generally mourn’d for his Sins in the Tears of the Tankard.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Grose Classical Dict. of the Vulgar Tongue n.p.: tears of the tankard stains on a waistcoat, supposed to be droppings of liquor.
[UK]G. Andrewes Dict. Sl. and Cant.
[UK]Lex. Balatronicum.
[UK]Flash Dict.
[UK]G. Kent Modern Flash Dict.
[UK]Flash Dict. in Sinks of London Laid Open.
[UK]E. de la Bédollière Londres et les Anglais 318/2: tears of the tankard, [...] taches de bière ou de vin sur un gilet.