If you’re in one week you are probably not used to it yet. I’ve struggled with the same thing, but now I actually find it easier to do mental work in the mornings because my body isn’t weighed down with food. Just stick with it, you need to adjust :)
I’ve found black cold brew coffee and then water with a small amount of lemon juice, salt, magnesium, and potassium incredibly helpful. The coffee suppresses my hunger and perks me up to stay focused. I know you don’t love coffee so you could try like green tea matcha. I’ve used that before as well and it cuts down my hunger a lot. The lemon mineral water keeps me feeling full and hydrated. Carbonated mineral water like Perrier was also I life saver in making me feel full and taking my mind off the hunger.
Plain water would always go through me so fast I wouldn’t feel hydrated, just more hungry and having to pee every 5 minutes lol. Also I think when you’re breaking your fast you may not be eating enough. I know it sounds counterintuitive but eating the right amount of calories you’d need for your goal body weight might be more helpful for your brain and body to run on.
The brain essentially needs 3 things to keep chugging along; oxygen, water, sugar (blood glucose). If you eat a big hearty meal full of Whole Foods, you might find you have better energy to work off when you wake up and start studying.
Ultimately IF is great but if it’s screwing with your education, park it until you’re in a place where you can do it again. You can still remain low-calorie and eat clean but if you need to eat an apple before you jam through a few chapters then hey man that’s ok.
Hope this helped. Feel free to ask me anything.