The only type of productivity which is good and spontaneous productivity. This happens from having overwhelming physiological energy and strength. For example, the energy you had after a really great night sleep. And perhaps a good caffeine buzz.
In other words when you are weak or exhausted, don’t force yourself to be “productive”. When you’re feeling weak and exhausted the most “productive” thing you could do is take a nap or try to go to sleep early, and abstain from further coffee or caffeine intake. Then wait for your energy to regain until you will spontaneously burst into some sort of virtuous creative activity.