This is very common when students get so bored during their daily preparation schedule so I would say better to take short breaks in your studies. Also, avoid having tea and coffee and the most important and the interesting one is you can devote sometime in your favourite hobby like football, basketball,PS, watching tv, playing indoor games etc whichever you like as this will make you feel fresh and after doing all this you can focus more on your preparation even if the topic is little boring.

Note: You can also go for short nap as this will give peace to your brain and you will feel refreshing as well.

Hope this helps!!!