The term “digestive” doesn’t sound terribly appetizing from the American point of view. Originating in the UK, the name just indicates biscuits which typically have a higher fiber (fibre) and wheat content than a regular biscuit. Additionally many are made with sodium bicarbonate which is meant to help with (long pause) digestion. The general flavor is akin to a graham cracker.
The best known brand is McVitie’s Hobnobs oaty biscuits. Delicious to be sure but too expensive at $5. Thankfully, Eti Digestive Biscuits with Oatmeal are a wonderful, far less expensive ($1.25) replacement. I like the lattice, stroopwafel like pattern on the biscuits. The taste is just as oaty. It provides a respectable crunch and crumbles agreeably in the mouth. These are fantastic with coffee. A product of Turkey, they come 15 to a pack. Because they don’t have the sweetness of a cookie you’re really only tempted to eat 2 at a time. As yet there isn’t a “store locator” to find the products but if there is a Middle Eastern store in your area, that may be a good start. For those in the Brooklyn area, the biscuits are available at Black Seed (576 Atlantic), two doors down from Fertile Crescent.
For those who are gluten free and vegan, here is a recipe for making a homemade version.