Depends on what you mean by "must do's". These days, we make up a list to choose from while we're at a particular place in the park, depending on circumstances of the day. Here are some of our choices in AK for places with particular dishes that have been highly-rated in the various food blogs and reports; YMMV. Listing good (not merely popular) dishes minimizes the chances of choosing an underwhelming food and overlooking a good one in a particular venue. Note: these are based on others' reports since we haven't visited recently; those marked with an asterisk* have been specially noted on some blogs. Also, we don't do as many table service restaurants as we used to (we generally go out of parks for good table service); counter service has improved dramatically in recent years (probably from the influence of many food festival kiosks). PLUS, everything's changing, so this list will be updated as our travels draw nigh.
Breakfast:
*Creature Comforts, Discovery Island counter: interesting breakfast sandwiches, Colossal Mickey Cinnamon Bun, Teavana teas
*Isle of Java, Discovery Island before Asia, counter: Tiger Tail Chocolate Twist, and Raspberry Streusel Muffin, Macaw special non-alcoholic drink
Kusafiri Coffee and Bakery, Africa near safaris: pastries including Colossal Mickey Cinnamon bun, Elephant ears, Pistachio Honey Croissant, and quiche
*Sa’Tulli Canteen, Pandora, counter: used to have interesting breakfast; check after full opening
*Tusker House, Africa: fixed price table, character breakfast, combination of American and African breakfast foods.
Yak & Yeti Local Foods Cafe, Asia, by Everest, counter: breakfast bowls and fruit salad.
Lunch/Dinner/Snacks:
*Flame Tree Barbeque, Discovery Island, counter (best BBQ in WDW): Ribs, Chicken, Pulled Pork platters, onion rings, *Loggerhead turtle non-alcoholic drink (basically Sprite with additions)
*Harambe Market, near Wildlife train, counter: Harambe Greek salad, ribs & chicken bowl,
*Yak & Yeti Restaurant, Asia, table: Fixed price meal with selections, lots of other dishes
*Sa’tulli Canteen, Pandora, counter: bowls and buns, including *cheeseburger Bao buns (highly-rated)
Dino Diner, Dinoland, counter: Fritos Pie, chili dogs
*Nomad Lounge, Discovery Island, counter: bowls, soup, bread service, tacos on the kids menu
Royal Anandapur Tea Company, Asia, counter: int’l selection of teas
The Smiling Crocodile, Discovery Island, counter: tamales, tacos