I work as a freelancer from home, so my answer might be less interesting to people at an office, but I've found that at home I'm mostly just doing the things I wanted to do at the office when I worked in one, but felt uncomfortable doing there. These include:

Taking short (15 - 30 mins max) naps if and when I need them, which pretty dramatically helps me creatively problem solve.

Going for a long-ish walk outside. This is by far the absolute best thing I've added to my days. I feel more energized after, I mentally and emotionally am much happier, and physically it made me slightly fitter. Plus it helps relieve some of the problems I know I'm developing sitting all day.

Podcasts. This one I only do when I'm taking a break, I can't focus and get into a flow listening to other people talk about interesting topics. Awesome for those walks though.

Chat with other developers and friends on slack or some other messenger. Usually at some point during the day I'll have a 15 minute flurry of messages with a developer friend about some side project or something we think is cool.

And finally, this one is half work half fun, but I'll research something I think is cool or would be useful. Might be a service, framework, product, methodology, anything at all. I probably spend an hour or so of my work day, every other day, on researching something that's not an absolute necessity to the work, but might benefit it. In some cases it's paid off big time. Mostly though it just keeps me happy, interested, and hopefully a little sharper.