Have A Few Meaning

(idiomatic) To drink enough alcohol to be slightly drunk

Example: 1983 Jaan Kross, The Rock from the Sky, p118
  'Course, once he's had a few, the old man'll gab the hind leg off a donkey.
1999 John Kaye, Stars Screaming, Atlantic Monthly Press, p119
  "Are you drunk?" / "I've had a few." / "You sound drunk," Maria said.
2004 Robert W. Wood, The Weeds of God, Omonomany, p68
  I drink to be exciting. It seems I say the funniest things when I've had a few.
2007 James D. McCallister, King's Highway, Screecher Creature, p28
  The phone at the lake house rings and rings, until my father's voice, very groggy — it's the way he sounds once he's had a few — is finally heard.