To unlock this, you need to eat the most expensive items in all of the restaurants in the game. If a restaurant has more than one item of the same price, you will need to buy the others as well. Make sure to carry some fish bait with you so you can eat them if your health bar is full.
For Smile Burgers, make sure that you are eating in the store and Pronto Bar in Kamurocho will need to be visited both during the day and in the evening for a slightly different menu. You can check your completion list under food and drink to see at which restaurants you've eaten at and what you already ate there.
Note: for Smile Burger, you only have to do one of the two locations since it shows up in both location's completion list.
Below is a list of all of the restaurants in the game and what you will need to order for the achievement.
Okinawa (Ryukyu):
Aqua Sky: Laphroaig 30 Years.
Blue Seal: Blue Wave, Pineapple, and Ube.
Quickly Tea and Boba: Peach Juice, Peanut Soya Bean, and Passion Fruit Juice.
Sam's Maui Grill: Deluxe Course Dinner 2.
Smile Burger Ryukyu: Giga Smile Burger Set.
Umachi Diner: Sashimi Platter.
Waraba Okinawan Soba: Tebichi Soba, and Rafute Soba.
Tokyo (Kamurocho):
Bantam: The Macallan 30 Years.
Café Alps: Original Beef Curry Set.
Earth Angel: Yamazaki 12 Years, and Hibiki 17 Years.
Gelateria Kamuro: Quadruple Scoop.
Kanrai: Special Limited Sirloin.
Kyushu No. 1 Star: Limited Ramen with the works.
Matsuya: Tuna Yamakake (L).
Pronto (Café - Daytime): Rich Egg Carbonara.
Pronto (Bar - Nighttime): Jamon Iberico (Ham)
Shellac: The Macallan 1946.
Smile Burger Kamurocho: Giga Smile Burger Set.
Sushi Gin: Awabi, and Uni.