If you're learning to juggle, you can absolutely get value out of 25 2-minute chunks during the day.
Even more complicated skills -- you may not be able to get things set up on a computer, but if you have a notepad you can take 5 minutes and jot down what you remember of whatever you're trying to learn. Next 5 minutes? Fill in the missing bits, or look up one of them.
I have lots of somewhat random skills that I've developed without really dedicating time at all -- like Tuuvan throat singing, or using the NATO phonetic alphabet -- practiced while driving, or in other chunks of time that seem to be already occupied (but are actually just constrained).
I'm not sure it can be done. The best way to maximize the use of small chuncks of time is to join them into rarer big chuncks of time.