My company does one day of work on Foss software each month to honor what the community does for us. We use nearly exclusively Foss software. My employees can freely choose which projects they support or what apps they build with that time. But usually they end up building or fixing something thats helping them with the job they are doing for a client or has annoyed them during that time.

Edit: everything be build, we publish under MIT license.

Edit 2: we are 4 people, I’m the only full time employee.