The current idea of sponsoring is to let people say "thank you" for projects where I'm involved in.

Open source is a hard hobby if it isn't supported by your employer.
In this case, the time on open source projects should be take outside business hours, mostly in evenings and on weekends, and that hurts.
It hurts, because you work 8 hours per day in front of a computer for your day job and, after that, you should stay in front of a computer for open source projects.

Now, keeping said above in mind, ask yourself whether the project has saved your time and/or time of your team. If yes, then highly-likely it has saved money to your employer or customers too.

If the project has helped to save time and money, is it worth supporting? What if the project died?
Try to discuss that with your team lead or manager.

Thank you.