I was once in a class being taught by an MD. I mentioned that I liked chocolate covered espresso beans. He told us a story about a classmate who brought a five pound bag of them to study for finals. The classmate ended in the Emergency Room for a caffeine overdose.

If I am sleepy, I take a nap. Thirty minutes to an hour will do.

If I am low energy or unmotivated I just power through with iced mint mate (coffee makes me sleepy) and spite.

if it's a task I have to do, I literally just make myself physically take the first step no matter how much I don't want to, because once I'm in media res, inertia kicks in.

Eat

It really depends, I try to listen to my body and think of whether I’ve had enough water and food and sleep, then fixing the issue accordingly by either hydrating, eating, or taking a short nap (or doing yoga nidra).

If none of those are the issue or if the nap is not possible, I will try some caffeine (coffee in the morning, cacao in the afternoon).

And if I have a chance, I will listen to some brainwave music that stimulates beta waves in the brain for concentration.

Finally, meditation helps me. It can be a nice pick-me-up and an opportunity to recalibrate and reset.

I've had a shitty time most of my life, my mantra is Back Straight, Chin Up, Eyes Open, and Keep Walking.

Tomorrow's another day. Sleep is the best 'reset button'.

Also, re the keep walking thing, it can be a lot easier to target nearby distance markers at a regular pace than to only think about the far away finish line.

"If I could rearrange the alphabet, I'd put U and I together."

Oh you meant stimulants.

My favorite pick-me-up is having a crepe in the morning. Taking strolls may help too if that counts.

Cold showers can help with that

I go for a run, after that I feel so much better. But it's not easy to get the run done some days

I remember: "It's better to do something than live with the fear of it". Then I get on with it.

I find that slowing down and just meandering through the things I have to do more slowly and comfortably, actually helps when I feel burned out. Maybe with some music. Feelings of urgency/tension in my body actually sap my energy way too quickly, before I can even get started. So I focus on managing stress preemptively.

This is not applicable to everyone or every situation but it made a big difference for me.

"How do you manage it?"
I don't.