I only know about the anime, so I'm basing this question on that. Toradora's anime aired in 2009. In 2011, a side story OVA was released with the Bluray collection of the series, titled "The True Meaning of Bento" (Bento no Gokui).
This side story has little to do with the main plot, so in principle it can probably go in a lot of places in the story. However, I'm wondering if there's a canonical answer for when these events occured (or if they are intended to be canon at all). I don't know if anything similar happens in the light novels or if there has been official commentary on where it falls (preliminary searches all didn't turn anything up), but either of those would be sufficient for this question.
Is this OVA canon, and if so, when in the story does it occur?