[Too]

While I've seen several examples of this being the only way to get out of never prioritized debt-cleanup that the team can't bother explaining to management in non-technical business-value terms. The reality is a sprint is always over-packed with stuff to do with zero room for side-projects and expecting people to work weekends on side-projects to solve company business needs is not exactly a sound strategy.

What one can do is is deliberately allot time to the team to work on any side-project as long as they are somehow attached to the business. There are ways to do this more organized, for example innovation-weeks or the famous Google-fridays.