There's a busy bar and nightlife scene in Colombo, and some coastal resorts, where you'll find lounges, clubs and many bars.
Elsewhere the only drinking 'scene' is likely to be a few guys clustered around the local 'wine shop', where hard liquor is sold from behind security grills.
Many colonial hotels (particularly in the Hill Country) have terrific, atmospheric old bars, often with wood panelling and a neighbouring billiard room.
There's not much of a clubbing scene in Sri Lanka, but Colombo has some impressive dance venues and promoters in Kandy put on the odd good night.
Elsewhere, Mirissa hosts lively beach parties and there's often some action in Unawatuna and Hikkaduwa too.
Note that smart dress (no sandals or singlets chaps!) is usually expected in Sri Lankan nightclubs. Men not accompanied by women are often denied entry.
Admission prices vary greatly but classy venues in Colombo cost upwards of Rs 1000 per person. Most clubs close by 3am.