Tonga is lively well into the evening, generally becoming suddenly very quiet at around 11PM. Expect to see people walking around until late. Beer and liquor are available from many outlets, including Fijian, Australian and New Zealand imports to complement the local brews. If you are keen to check out native drink, try Kava something like liquid novacaine at least once.
The local beer is called Ikale and is sold in 330 ml bottles in most restaurants and bars 4.50-5 Pa'anga. Or you can buy the same bottles from one of the many 'Chinese' roadside shops or a supermarket for 2 Pa'anga or less. Imported beers are mainly from Australia although there are also some from Europe. Most are sold in 330 ml cans or bottles.