Green’s Dictionary of Slang

(US) stimulated by alcohol but not drunk.

1928		M. Prenner ‘Sl. Synonyms for “Drunk”’ in AS IV:2 102: basted [...] tipsy, tuned, woozy.
1931		A. Hardin ‘Volstead English’ in AS VII:2 88: Terms referring to the state of intoxication: [...] Verbs: Tuned.
1953		R. Chandler Long Good-Bye 19: There was the usual light scattering of compulsive drinkers getting tuned up at the bar on the stools.
1966		Current Sl. I:1 5/1: Tuned in To have something to drink, but not enough to cause intoxication.