There are no bars in Kuala Tahan as it is a Muslim village. Chess Corner, near the Tembeling Riverview Guesthouse is a nice bar style cafe where locals sing songs and play the guitar at some nights. However, this 'bar' does not serve alcohol. There are also several cafes across the Tembeling River which a reachable by a quick boat ride.
One local drink you should try is the "Sirup Bandung", which is a blend of rose syrup and milk. It is a tasty concoction to drink after a day's trek.