Taking a good break
A break works when you leave the task. Staying in the chair and opening another tab keeps the work in your head.
For a short pause, about five minutes is the length people pair with a 25 minute block. Get a drink and step away from the desk. Leave the book open. You will be back before the page has gone cold.
If something might be urgent, look once and put the phone down before you sit, because a message thread will keep going for as long as you let it.
After a few blocks
After a few blocks, take a longer pause. Fifteen or twenty minutes is enough to eat or to walk outside. Attention thins after repeated sittings. You can feel that even when you would rather keep going, and the longer pause is there for that reason.
Cuppafocus times the work. When the session ends, the day is already marked, and the break does not run inside the timer. Make the tea, or watch a clock for a few minutes, then start another session if you still have work. The next block can be a different length. A hard problem might want 45 minutes. Reviewing a page of notes might want 15.
If you are hungry or the room is cold, the plan will fray. Deal with that before you start, or use the pause to fix it. A cup of tea is a sound use of those five minutes.
The 25 minute block and the five minute pause are the usual Pomodoro timings, described in How the Pomodoro method works. When you want to work again, go to the home page and start the timer yourself.