The two-minute email
You sponsored the team, donated the gutters, fixed the website. Most businesses stop there and get a name in a photo caption. Send this instead. Fill in the blanks and copy.
Subject: Thank you, and one small ask Hi [their name], Thanks again for letting [your business] be part of [organization]. We donated a new roof for the community center, and it meant a lot to the team to help. One small ask: could you mention [your business] on your supporters page, or in the post about the project, with a link to [your website]? It helps people find us, and it is how most of our community work gets noticed. Happy to send a logo, a photo from the day, or a couple of sentences if that makes it easier. Thanks, [your name]
When to send it
The same week, while the story is fresh and the photos are being posted. Ask for the mention first and the link as part of it, never the other way round.
If they say yes, send the logo and a line of text right away so it takes them two minutes too.