derived from the English 'sex maniac'
Mukha kang manyakis.
You look like a sex maniac.
Mukhang manyakis ang bagong dating.
The newcomer looks like a sex maniac.
Parang manyakis si Alberto.
Albert is like a pervert.
Baka maging manyakis ang kapatid mo.
Your younger brother might become a pervert.
This is often used for men with a crazy-for-sex look on their faces and also those who move rowdily as though they're about to explode with sexual energy and those who behave improperly around women.