ispijati

1. to drink up; to drain
   Svako jutro ispija čašu vode na prazan stomak. — Every morning he drinks a glass of water on an empty stomach.
2. (of coffee, drinks) to sip; to have a leisurely drink
   Satima smo ispijali kafu u bašti kafića. — We spent hours sipping coffee on the café terrace.
3. (of strength, energy) to drain; to sap
   Ovaj posao mi ispija svu energiju. — This job is draining all my energy.

The perfective is ispiti; ispijati kafu is a typical phrase for a leisurely coffee with friends.