Green’s Dictionary of Slang

(US campus) a bracing drink of alcohol.

1827		J.F. Cooper Red Rover 124: ‘Bitters,’ ‘juleps’ [...] ‘fogmatics,’ etc.
1837		‘Plunder Creek’ in Bentley’s Misc. Feb. 124: They [...] couldn’t give me a beaker of egging, or gin cock-tail, or a grain of sangaree, or any other fogmatic.
1844		Stirling Obs. 19 Sept. 3/3: [from US press] Drunkeness Defined — [...] phlegm-cut, fogmatic.
1853		Dundee, Perth & Cupar Advertiser 23 Dec. 4/4: This is dreadful weather [...] it is sometimes necessary to take something by way of a fogmatic.
1863		Preston Chron. 22 Aug. 6/4: A pennyworth of fogmatic mutilation.