The coffee is ready to drink为什么不用被动

主动表被动的用法,
例如 主动形式表示被动意义
　1)wash,clean,cook,iron,look,cut,sell,read,wear,feel,draw,write,sell,drive…
　　The book sells well.　　这本书销售得不错.
　　This knife cuts easily.这刀子很锋利（好用）.
　2)blame,let(出租),remain,keep,rent,build
　　I was to blame for the accident.
　　Much work remains.
　3) 在need,require,want,worth (形容词),deserve后的动名词必须用主动形式.
　　The door needs repairing.= The door needs to be repaired.
　　This room needs cleaning.这房间应该打扫一下.
　　This book is worth reading.　这本书值得一读.
　4) 特殊结构：make sb.heard / understood (使别人能听见/理解自己),have sth.done ( 要某人做某事).希望对你有所帮助.

ready 是形容词，不是及物动词。不可以用被动语态。

to do 不定式做定语。表示将来时。“等待被喝的”like " i have something to do"还没有做的事情