there are exact words for sleepy, but trust me, even native speakers cant understand you, if you use those. generally we say, neend aa rahi hai = feeling sleepy

Nidralu or Nidragrast. However these are pure Hindi form of Sleepy. Which is not being used. We use "nind aa rahi hai". There are a lot of words in Hindi which we do not use as such. So we have made a lot of different words which is much easier than these typical Hindi words. Like if we say Train, it's pure hindi name is "lauh path gamini" but since not easy to use it in normal conversation, we use "rail gadi". But still these are also the Hindi words and are more simplified for of the complex words.

sleep = सोना Sōnā / नींद nīnda

ha ha ha.....lol.........why sleepy in hindi ;-)