TL;DR: before each Pomodoro, think for 5 minutes about the Pomodoro ahead. It improves your work efficiency and mental wellness.
ADHD. My solutions are two: (1) treadmill desk, which occupies jitters while pumping blood-flow and endorphins for optimized focus; and (2) the Pomodoro Technique. Pomodoro alone is enough to transform your work life; but it takes a lot of discipline, so many people stuff it into their "should" pocket. I've found that initializing it with a "thinker" (5 minutes of planning the Pomodoro session at hand) improves the effectiveness and focus of the work session, making Pomodoros less painful and therefore less likely to be avoided. These thinkers also double as meditation; and similar to fitness desks two-birding gyms out of your life, thinkers can two-bird that daily task of meditation you've been avoiding.
Quick recap on Pomodoro. 25min of work, 5min break. That 25min work session should be hardcore and uninterrupted - no texts, email, Slack - much less Reddit, the fridge, etc. Unless your session is dedicated to emails and Slack, of course; you set the rules, just focus without distraction. And the 5min break lets you catch up on all the other stuff, go to the bathroom, grab a coffee, etc. Rinse and repeat. Done perfectly, an 8hr day "loses" 80min of work, but not a chance that's a loss compared to standard distracted non-flow workdays. In reality, nobody can go 25, 5, 25, 5 perfectly through the day. You'll fudge the hell out of this due to the unpredictability of work days, but try your best.
The modified version is simple: 5min thinker, 25min work, 5min break. During the thinker, you close your eyes and think deeply about a few things. Where did you leave off before the break? What should you do next? What can you accomplish during this Pomodoro? Is that the right thing to focus on, or did you maybe go down a rabbit-hole last Pomodoro, and it's time to switch gears? Now imagine a play-by-play of actually solving the tasks ahead of you for this Pomodoro. As soon as the 5m timer goes off, stop thinking; doesn't matter how deep in thought you were, it's time for action, and you'll have time to think through more of this next thinker.
Efficiency. The problem with Pomodoros is the ramp-up. All this stuff about how hard it is to get back into work after a distraction, and the 5min break is definitely a distraction. Thinkers strong-arm your brain back into gear. Further, this process called imagery / visualization / mental rehearsal is known to improve throughput and performance, as studied in sports. Your work will be stronger.
Flow. 5min doesn't seem like a lot, but in meditation terms, it really is. When the timer's up, the full 25min will be nothing but truly-focused delivery on the rehearsed play-by. Imagine a Hollywood-film Kung-fu artist closing his eyes and visualizing the sword-play through 100 foes. Bam, he opens his eyes and springs into action.
Enjoyability. Works sucks, I hate it. Meditation (this is meditation, see below) improves mental wellness. The proximity of meditation to a task improves equanimity in its handling. I'm not suggesting you'll suddenly love working; just that you'll hate things less, proximal the thinker. Meditation improves your mental wellness, and this much meditation will transform your handle on the day.
A lot of my life-hacks are what I call "two-birders". Treadmill desks are an example: by walking or stepping at your desk, if you've accumulated enough active-zone minutes through the day, you can skip the gym. This saves time and money; never mind the improvement on your energy, posture, focus, etc. Thinkers improve the effectiveness of your Pomodoro regime, and make it easier to adhere to it (by making Pomodoros more efficient and enjoyable); and this is because thinkers are meditation.
Meditation is any deep focus. It's a fuzzy word, and contenders would champion "attention without intention." This form indicates non-thought, like focusing on your breathing or the imagery of a flame. But many practitioners agree that "without intention" isn't necessary, and is usually there to make the practice more accessible. Any form of legitimate focus counts as meditation. This can be thinking through statements of gratitude, affirmations, running through memorization exercises; and yes, thinking about work. If this ruffles feathers, I know why: you're familiar with "thinking" about work as something that brings you anxiety and distraction. That's not focus (meditation), but rumination (its opposite).
Rumination is the mind doing its own thing "on accident." Daydreaming. Mind-wandering. Cycling over unresolved business in an attempt to earmark its priority. The part of the brain active is called the Default Mode Network, and is associated with anxiety, depression, and all the baddies. Meditation moves primary activity from the DMN to the Task Positive Network (DMN's antithesis), strengthening that area and improving mental wellness. This is why the solution to difficulty sleeping, caused by racing thoughts, is to count sheep. Counting sheep is meditation.
Prove the difference to yourself by performing a single thinker right now: 5min of planning your day, but without letting distractions enter your mind. Use the usual practice of letting intrusive thoughts drift away, and returning to the focus. Actually plan your day through rigorous focus, and note how you feel after. Also note any improvements to the day's final outcome; how much more you've delivered on intentions than usual.
Now. It's recommended we meditate 20min each day, the mental analogue to 20 active-zone minutes of exercise. On a perfect day using this modified Pomodoro structure, that's 13 * 5min = 65min. That's an hour of meditation each day. You're going straight to cosmic bliss.
So you're not just improving a Pomodoro's effectiveness via rehearsal (temporary); you're improving your work capacity by strengthening your prefrontal cortex through meditation (permanent). That's a lot of birds.