tap

card 1 of 10 · context meaning

What is the meaning of 'tap' in this sentence?

Here he produced a decanter of curiously light wine, and a block of curiously heavy cake, and administered instalments of those dainties to the young people: at the same time, sending out a meagre servant to offer a glass of "something" to the postboy, who answered that he thanked the gentleman, but if it was the same tap as he had tasted before, he had rather not.