Dear …
Re: __(Type of Event/Program/etc.)__ - Sponsorship/Participation Request
We are in receipt of your request asking for sponsorship and participation from our company in your __(type of program)__ program this year. While this __(type of event or cause)__ certainly appears to be a worthwhile __(event/program/cause/etc.)__, we regret to inform you that __(Name of Company)__ will not be participating in your program this year. In addition to our charitable donations budget being fully extended for the year, we are not currently in a position to offer the human resources required for participation in the __(program/event/etc.)__ as outlined.
Perhaps there may be an opportunity for us to revisit this another time. In the meantime, however, we do offer our best wishes to you and __(Name of Organization)__. May you achieve great success with your __(type of program/event)__ this year.
Best wishes,