Do Cylon Leaders in Battlestar Galactica (Daybreak expansion) draw an extra card in sickbay?
No, Cylon Leaders are restricted to one card in Sickbay.

From the Daybreak rules


  An Infiltrating Cylon Leader draws one extra Skill Card from
  within his Skill set during his “Receive Skills” step for a total of
  three Skill Cards.


Hence, they only receive an extra card if they are receiving their normal 2 cards.  Sickbay overrides it to only allow one card per character in Sickbay.

The rules also note that the Infiltration card is a "summary" of the Infiltration rules.