This is the 9344th most frequent Japanese word.
眠く
"Sleepy" (adjective).
In this sentence, '眠く' is used to describe the speaker's state of feeling sleepy, indicating a physical or emotional condition.
最近、夜更かししすぎて毎日眠くなります。
Recently, I’ve been staying up too late, and I feel sleepy every day.
Here, '眠く' combined with 'ならないように' reflects a preventative desire to avoid the state of sleepiness during class, connecting action with condition.
授業中に眠くならないようにコーヒーを飲みました。
I drank coffee so I wouldn't become sleepy during class.
The usage of '眠く' in this sentence denotes the arising of sleepiness as a reaction or result of the meeting's duration.