There are two flavors I have a hard time acquiring: sweet and sour. Today, I'm just going to list what I've found for sour, for others in that situation.
Vinegar and citrus are what most folks use for sour. Vinegar is out for me right now, and citrus only in very small amounts, as I have a limited supply from a couple farmers. So, here's a few other things I've come across that may work.
Sour Tasting Ingredients:
1. French sorrel - this is a green leafy herb that has an extremely sour taste. I have not attempted to use this much, usually just in salads, but it works well there. There is a dairy-based Sorrel sauce for salmon that uses this herb in large amounts.
2. Amchur powder - I can't use this, but if you can, it's powdered mango and usually available in Indian grocery stores. Frequently used in Indian cooking, so it blends well with curries, soups, and stews. I imagine you could figure out how to make this yourself with a dehydrator, if you can eat store-bought mangoes or grow them yourself.
3. Under-ripe (green) tomatoes - for sauces and chutneys, these can add a nice sour bite. Sometimes these seem to lose some of the sour when cooked for a long time, but that may just be my own perception and not reality. Hard to find these when they're not in season, though, and I have the best luck at Farmer's markets, in the southwest USA. In the deep south, I imagine they might be more readily available at a regular market.
4. Tomatillos or ground cherries - also for sauces, nice sour bite. These are the green, tomato-like veggies that look like a green tomato with a papery thing coating over them that peels away easily.
5. Tart fruits and veggies - green apples, cranberries, and rhubarb are the three that seem of the most use, although cranberries and rhubarb are fairly seasonal.
6. Grape leaves - these are edible and have a sour flavor as well.
7. Thai Red Roselle - This plant eventually has small fruits that supposedly taste very like cranberries, so they might be a good choice for sour tastes, too. The leaves are good for a sour tea, too, according to various sources. I am currently growing these, but have yet to try them, so I couldn't say these are certain to work.
Note: French sorrel and grape leaves both contain higher levels of oxalic acid, from what I'm reading. If you are prone to oxalic acid kidney stones, you might investigate whether these will be safe for you.