The original 25 minute with a 5 minute break is the classic. I would advise trying the classic first.
Here’s some possible variations that might work with practicing music. Some of obviously more intense than others. It’s just me brainstorming, so feel try out your own variations.
Pick a bunch of songs that you like and are working on. Group them into 25 minutes. Play along to the songs. When you’e played through the playlist, take a break.
Pick one song and repeatedly play along with the song. If you know the song is 5 minutes, for example, practice along 5 times.
Develop a warm-up and basic practice routine that takes about 25 minutes. For example, I warm-up my hands for about 5-7 minutes by slowly strumming. Next, I’ll play along to a couple of songs, usually ‘So What’ (9 minutes). Then I’ll do vocal warm-ups for 5 minutes. And finally I’ll practice soloing over some basic changes, swung and latin. That’s about 25 minutes.
While there may be something special about 20-25 minutes. You can be easy on yourself. For example, use one of the 5 minute practice ideas and take a 5 minute break between each one.
You can use the breaks to do some other type of work or task. For example, practice 20 minutes, work out/stretch 10 minutes, relax 5 minutes. This isn’t the Pomodoro Technique, but it’s worth thinking about.
If you have multiple projects, you can switch between practicing music and your other project. This in effect will give you 30 minute breaks from each project (the musical project and the non-musical project).
This is especially good for tougher musical tasks. For me, the toughest practice item would be transcribing a solo. It’s tedious for me when I have to slow down the music and listen many times to pick up the melody. It’s definitely worth it. But tough mentally.