I would say it's personal. Other factors could play a role but often insulin resistance is highest in the morning and/or you could also have a slight dawn phenomenon effect.
For me, with a pretty bad dawn phenomenon effect, the result is that if I drink kefir (fermented milk) in the morning it can send my BG up by an extra 3 points. When I eat it in the late afternoon it barely shows up.
Generally I can get away with more "naughty" foods later in the day. But also generally, on the rare occasions I do, it comes back with a vengeance the next morning.