If you are planning a trip to Hawaii one of the most fun and rewarding things to do while there is to visit a local hawaiian farmers market. The reason is because you will find things that you have never tried before most of which you might never have seen before. The quality of the produce is incredible and they have tons of stands with foods you can try. It’s a great place to go for lunch if you want true native food.
Two items that are very popular are freshly squeezed lemon aid and crepes. Neither of these things is native to the island but they are incredible. The lemonade is usually made from fresh sugar cane. They grind the stalks to order and then press a fresh lemon and mix it over water. This has higher nutritional value than the stuff you buy at the store. Not only does it taste great but it also has no fructose.
The crepes are fun to watch getting made to order. There are the typical kinds with Nutella or island favorites like coconut and pineapple. This nail tech from an Arizona Salon who was on vacation didn’t try anything fancy, instead, she went with a basic crepe with some powdered sugar. Ironically her nails are fancy but her culinary preferences tend to be simpler. Either way, her fingers, and the crepe look great. 
Almost every market you go to will offer freshly made lau lau which is Hawaiian soul food. Usually pork but all kinds of meats or even things like sweet potato are wrapped in taro leaves and steamed until tender. You eat the entire thing the leaves are healthy. It doesn’t get more authentic or local than Lau Lau. It’s tough to find but real authentic Hawaiian restaurants will serve it if you can’t make it to one of the local markets.
Not only can you expect find tons of local produce fruits and vegetables but generally there will be live music. In other areas of America Farmers markets usually have a lot of art and locally made trinkets but in Hawaii this is more about food. The market of stuff from the farm.
The weather is always nice on the islands of Hawaii so that’s what makes these kinds of events so popular. Not just with tourists but with the locals. When you are on vacation give it a try and you will instantly realize why.