formal: mengantuk, slang: ngantuk = sleepy
formal: lelah/capai/letih/pegal/pegal-pegal, slang: capek/pegel/pegel-pegel = tired
Capek is the slang word for capai, it is used in spoken indonesian and doesn't considered as impolite. While pegal/pegal-pegal is best used when you feel tired and aches all over your body. Exhausted doesn't have equal translation in indonesia, we just simply said very tired (formal "sangat lelah" or slang "capek banget")
i hope this helps! if you have any question about indonesian, feel free to ask me :)