In some formal communication, I would like to use that phrase to indicate how reliable my product is, because we use it on a regular basis, and thus serve as a reassurance.
Here's a definition from Joel Spolsky:
The term “eating your own dogfood,” in the software industry, means using the code you’re developing for your own daily needs: basically, being a user as well as a developer, so the user empathy that is the hallmark of good software comes automatically.
So you can write, "We are users as well as developers of our own product; it's a reliable part of our daily workflow," or however it is you use it.
An alternative phrase: you're putting your money where your mouth is. You're not just talking about your product, you're investing in it as well.
I appreciate that this isn't very formal. Having said that, it occurs to me that however you phrase this sort of statement, the audience may get the impression that you're rather desperate for them to trust you. Attempting to make it seem more formal might have the opposite effect, unless backed up with an example, e.g. something along the lines of
At [company], we use [product] for [use case].