The main reasons students feel sleepy while studying are studying lying down, heavy meals, poor night sleep, and boring passive reading. Fix those and the drowsiness largely disappears. The fastest single change: sit upright at a desk in bright light, never study on your bed.
Study actively, not passively. Just reading lulls the brain to sleep. Solve problems, write notes, test yourself, or say things aloud. Activity keeps you awake far better than silent reading.
Take short, regular breaks. Study in 40 to 50 minute blocks with a 5 to 10 minute break to stretch, walk, or splash water on your face. A quick walk re-energises you more than pushing through.
Watch what and when you eat. Heavy, oily meals make you drowsy. Eat lighter, and keep water nearby, because even mild dehydration causes tiredness. A glass of water often beats a cup of coffee.
Example: A Class 12 student in Chennai who kept dozing at night shifted tough subjects to early morning, studied at a desk, and took a 5-minute walk every hour. The sleepiness stopped being a problem.
Fix your night sleep. If you are not getting 6 to 7 hours, no trick will keep you alert, because sleepiness while studying is often just sleep debt.
One practical tip: When sleep hits hard, stand up and study aloud for a few minutes, or switch to the most active task (like solving questions) rather than reading. Motion and activity wake the brain.