Green’s Dictionary of Slang

1. (also befogged, fogged-up) drunk, tipsy.

1914		R. Tressell Ragged Trousered Philanthropists (1955) 284: ‘Oh, of course everybody’s an idjit except you,’ sneered Crass, who was beginning to feel rather fogged.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 212: fogged, intoxicated. ‘He walks like he might be fogged’.
1921		Western Times 10 June 9/1: [headline] Fogged By Drink.
1933		‘William Juniper’ True Drunkard’s Delight.
1945		J.T. Adams Mountain Murder 23: Haynes saw at a glance that Clary was in his usual condition—befogged with moonshine.
1968		D. O’Grady Bottle of Sandwiches 43: My fogged-up brain.

2. under the influence of a drug.

1949		Monteleone Criminal Sl. (rev. edn).
1985		K. Vacha Quiet Fire 65: You just can’t take that many drugs [...] you feel like a zombie. And I said, ‘Bullshit, I’ve got too good a mind, I don’t like being fogged.’.
1995		C. Hiaasen Stormy Weather 242: He was too fogged from the pills to improvise.