How can you prevent sleepiness while studying?

Taking breaks  in between your studies.2.Find the most  comfortable place  of study that will increase you alertness. 3.Identify things that trigger sleepiness for example for some studying sitting on a bed and avoid such. 3 Find things that boost your alertness for example some people become  more alert  after drinking coffee..4 planning your work and being organized to avoid feeling being overwhelmed which may lead to feeling sleepy

• Having not a regular sleep schedule. Try to sleep continuously for 7–8 hrs and fix a bed time schedule. Most people with sleep problems don’t have good sleeping schedule. Go to bed and wake up at the same time daily.
• Exposure to more blue light after sun set. Avoid mobile, computer etc 1 hr before bed. Use blue light filters for such devices. Example….f.lux for PC/Mac, night owl for android etc.
• Place mismanagement. Don’t use you bed/bed room for study. If you have just one room, don’t study in bed. Get a chair-table and arrange it such that bed faces your back during study.
• Interest. Sleepiness can be caused by lack of interest in the subject/topic of study. Try to develop interest in the topic. You can view videos and tutorials related to your topic and also several other audiovisual tools available.
• Breakfast. Breakfast is crucial. Several of my friends have recovered from study-time fatigue just by having regular breakfasts.
• Heavy meals. Avoid heavy meals. Take rest after meals.
• Caffeine. Take coffee/tea if above things are not the problem. Refer to caffeine dosage guidelines and avoid addiction.
• Physical weakness/fatigue. Never stress your body physically before study. If you are physically weak, see a doctor.
• Ventilation. Proper oxygenation is required for active brain functioning. Get proper ventilated study place.
• Temperature. High temperatures (>30 deg C) can make one sleepy. Try to make room cool if possible.
• Hydration. Our bodies require good hydration no matter what we are doing either physical or mental. Good hydration helps deliver good amount of O2 to your brains which helps keep it active.

When I was a student, that was 25 years ago, I never slept at studies. I liked my classes and I slept at night, so at a daytime I was full alert 

First and foremost, have sufficient sleep at night, that is atleast six hours but standard is eight hours. The during study time have breaks and a certain period of time and also keep interchanging tasks. The study environment should be condusive, i.e. well ventilated, well lit and not noisy.

Make sure the room you are studying in has enough fresh air and are well lit.  If you feel sleepy, try walking around in the room and repeating the facts out loud.  A short break or walk in the garden can sometimes do wonders.

Ways to avoid sleep when studying:

Do not sit on the bed during school:

When you sit on your bed to study it is normal for you to sleep so sleep and say goodbye to the book.

No tickets for classes and hard materials at night:

At night your body and brain are more idle so you have to leave the complex chapters and choose the easy and interesting classes and prefer to study your favorite materials during the night.

Moving in the room: 

It is very useful to move from place to place in your room when you feel drowsy.

Avoid soft drinks and energy drinks:

Most students make the mistake of drinking too much soft drinks while studying. Soft drinks make the individual less attentive and lead them to a lower concentration towards study.

Most of us feel drowsy during the study, the first thing he does, either to sleep and to prepare him to drink stimulants "caffeine." Tea and coffee can be replaced with fresh juices and if you can not do without them you can drink tea and coffee but not sugar.

Siesta :

Siesta is very good for those studying at night. An afternoon nap plays a vital role in getting rid of sleep.

Study aloud:

Listening to your voice while moving around the room has an effective role. It may not work with everyone but has proven many results with students that have a positive role.

healthy food :

If you want to avoid sleeping while studying, you need to make a change in your eating patterns. Instead of eating three large meals a day,5 small meals are recommended throughout the day. These meals will constantly provide the body with nutrients and vitamins that will help keep your concentration and also avoid fatty meals because eating heavy meals makes the mind and body slow and lead to inactivity.

Eat Omega3 :

Omega3, among other things that help keep the person awake. If you feel drowsy, eat omega-3 rich foods Such as fish, fish oil and salmon.

Magnesium supplements:

Many of the causes of drowsiness during study, due to the lack of essential vitamins and minerals in the body. In case you do not get Enough magnesium in your diet, you have to take magnesium supplements.

One of the things you should also pay attention to and do not neglect to drink a lot of water, and be lighting Good in the room.

Get enough time to sleep for at least6 hours a day. This reduces your sense of sleep.

When I have a long study session, I try to set up different tasks and switch back and forth at intervals so I don't get tired of working on any single part of the study session.  I have found that when I do this, I can keep my concentration for a longer period of time and study more effectively.

preventing sleepiness starts with having a good night and enough hours that our body needs.

I tried different techniques until I realize that my excessive sleepiness caused by stress. Among a great number of articles and resources on the web, I've found only a few that worth the attention, for example, this article about narcolepsy. It's not only about studying, but it is also about living with narcolepsy. 

First you should find the reason of sleepiness, after that based on the reason i will try to solve it , but usually drinking coffee and reduce use of fat and diary late at night could help.