I try to spend 45 minutes a day on meditation (as recommended in The Mind illuminated), though I probably average closer to 25. You are unlikely to get anything useful done in 25 - 45 minutes of side project time.

A side project is going to take a long time especially as your time on it is likely to be split up a lot more - so effectively far more context switching. All the other activities (except meditation) can be done more as a one time activity.

(I have started multiple side projects, but then I get busy with other aspects of my life and they get forgotten about).