Fresh fruits and vegetables are awesome, aren't they? I totally think so. I also think being able to get local produce is pretty awesome and there's no better place to get such things than at a farmers' market. We make a point to hit up markets wherever we are if we can. Sometimes, they are just cute little roadside markets that sell yummy things, but often there are many merchants gathered with their goodies in a formal market. Some are open everyday and some only sell on certain days. Our local farmers' market, which we are lucky to be very close to, is open only on Saturdays and then on Wednesday evenings during the summer. A lot of markets we've been to have limited days like this, but they are worth the effort if you can go to them.
Try new foods
I'm all for trying new foods. How else will you know if you like something? This is the next best thing to picking it yourself. It's super fresh and probably a better deal than getting it at the supermarket. Likely, it doesn't have pesticides on it either. Produce I buy at the farmers' market always tastes better than the same things I buy at the store, which is why I frequent ours two or more times a month. Local foods are a great way to learn about a place, too. Have you ever tried dragonfruit or fresh papaya? I have, in Hawaii!
Buy staples for meals
You're staying in a vacation rental, right? Of course you are, because you like having more room and saving money. Well, that means you have a kitchen and can make your own dishes. If it works out, head to the market near the beginning of your trip and then you have fresh veggies, spices and herbs to make dishes with. Woo! Not sure if you can make entire meals with what you find? You can, and soon I can show you as I'm currently working on a travel cookbook. It'll be full of recipes on things to make before your trip and while you're on it.
Pick up fixings for a picnic
Travel during warm weather deserves to be celebrated with a picnic! If you can't find bread, cheese and meats to make sandwiches with, I'd be really surprised. Grab a bunch of carrots or other favorite veggie to have on the side. Delicious!
Find food products you can take/ship home
You know those fancy jams, pastas, dried fruits, candies and stuff people always bring home with them? You can do it, too. Sure, you can buy them in specialty shops, but at the markets they are normally all in one place and you can sample them to know what you actually like. If the items are liquidy, like jam or wine, put them in your bag and check it back home, unless it's cheaper to mail them back, then do that. It'll be like Christmas after you get home.
This might not be the norm, though I've seen food trucks and carts more often than not at outdoor markets. Ours has a few and also a coffee truck, which makes morning so much better when you're up early enough to find a parking space (people here really like the market) and aren't totally awake enough to drag around your heavy bag of freshness.
Meet with the locals
Engaging with the locals is a fantastic way to learn more about your destination. You can ask them questions about good places to eat (when you aren't making your own food) and cool places to visit. You may even make a new friend. If you're in a place that speaks a different language, this is a great way to practice, too.
Support the economy
Supporting the local economy is important. Even better than shopping small businesses is giving money directly to the growers and makers of things. You purposely chose your destination for a reason, so maybe spend more time going to local shops and restaurants than chains and you'll be doing your part as a good tourist.