Tea or coffee laced with spirits, a cup of tea or coffee qualified with brandy or whisky.
“Deacon Bearcliff ... had his pipe, and his teacup ... laced with a little spirits.” —Sir W. Scott: Guy Mannering, chap. xi.
“Dandie ... partook of a cup of tea with Mrs. Allan, just laced with two teaspoonfuls of cogniac.”- Ditto, chap. iii.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894