I had wondered the same thing since I love sweet green tea in a can and so I did a little reading. I came across this article at Prevention’s website:

The article answers your question in more depth than the summary I’ve included. In the article they breakdown the antioxidant power of various forms of tea preparation. Antioxidants are the chemicals that supposedly pack big health benefits. Here is the chart that summarizes their findings:

Antioxidant Power
Preparation Brand Power Rating
Overnight fridge
tea Salada Green Tea (bags) Excellent
Hot water-brewed tea Salada Green Tea (bags) Excellent
Tetley Original Blend (black tea, bags) Excellent
Liquid concentrate tea Nestea Liquid Concentrate (green tea with honey) Excellent
Overnight fridge
tea Tetley Original Blend (black tea, bags) Very Good
Bottled Tea Honest Tea Moroccan Mint (green tea) Very Good
Lipton Iced Tea (sweetened, no lemon) Very Good
Snapple Iced Tea (sweetened, with lemon) Very Good
Arizona Iced Tea (sweetened, with lemon) Very Good
Powdered tea Crystal Light Peach Tea (sugar-free) Very Good
Cold water-brewed tea Lipton Cold Brew (black tea, bags) Very Good
Bottled tea Nestea Iced Tea (sweetened, with lemon) Good
Powdered Tea Nestea Iced Tea (unsweetened, with lemon) Good
Liquid concentrate tea Nestea Liquid Concentrate (sweetened, with lemon) Good

Sources: prevention.com
Q: Is instant green tea as good for you as brewed green tea?
I recently gave up my Diet Coke addiction in favor of diet green tea. I usually buy the small packets of Lipton that you add to a bottle of water. Just wondering if it is healthy, or just a bunch of chemicals. (2 answers – asked 25 months ago)
A: Instant tea has fewer antioxidants than brewed tea.
I’ve read in a number of places that brewed tea has a higher concentration of antioxidants and is generally better for you than instant tea. Below are two links I found via a quick Google search.

Instant tea has fewer antioxidants than brewed tea. This is because processing of tea reduces its antioxidant content, and instant tea is more highly processed than brewed tea. Decaffeinated tea also has fewer antioxidants than caffeinated teas. Brewed tea is a rich source of antioxidants, including flavonoids and catechins. Antioxidants are natural compounds found in many foods. These compounds may protect against tissue damage from free radicals, which may lead to diseases such as cancer and heart disease.

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Bag it. When Consumer Reports tested the antioxidant punch of 15 brewed, bottled, and instant teas, it found most teas brewed from tea bags scored highest in antioxidant content. In fact, the magazine reported, “Brewed tea appears to have more antioxidant action than almost any whole fruit or vegetable — and more than most commercial fruit or vegetable juices, too.” But iced teas from mixes and bottle are a decent second choice; they contain a “good deal” of antioxidants, according to the magazine. Just watch the sugar content.

Dunk the bag. Continuously dunking the tea bag as the tea steeps seems to release far more antioxidant compounds than simply dropping it in and leaving it there.

Add lemon. One study found that the addition of lemon to plain tea increased its antioxidant benefits. That makes sense, since lemon itself contains antioxidants.

Sources: Sources are listed above.
Q: Have you ever gotten sick from bacteria in sun tea?
I just ran across that you are more likely to get bacteria from the water by brewing your tea in the sun apossed to boiling it .It takes up to 195 derees f. to kill the bacreria and the sun will only getup to 145on your tea or close…… (4 answers – asked 23 months ago)
A: Sun Tea

I drink a LOT of sun tea, for years, and have never gotten sick from it. And as I mentioned in the last answer, I don’t even make it in the sun–just water and tea bags in a jar in the refrigerator. No heat, no sun, no bacteria killing, I guess.

I’m sure that the research is probably true, but start with a clean jar and refrigerate it and use it within a day or so and you should be fine. I have heard of people in restaurants getting sick from

Instead, follow the recommendation of the National Tea Association and use the same process to ‘brew’ iced tea in your refrigerator overnight. It’s far more economical than commercially prepared iced tea, and you can make it the night before with no cooking or boiling needed.

Refrigerator Tea
1 gallon cold water in a sun tea jar or large lidded glass jar
9 standard-sized tea bags (regular or decaffeinated)
Honey to taste, if desired

If the tea bags have tags, remove them first. If they have strings, you can tie all the strings together to make removing the tea bags easier. Put the tea bags in the jar, pour the cold water over the bags, and cover the jar with the lid. Refrigerate overnight. Remove the tea bags (a slotted spoon makes it easier). If you want to sweeten the tea, add honey to taste just before serving, stirring until dissolved. Store in the refrigerator and discard any unused tea after 24 hours.

Variations

Loose tea: To use loose tea instead of tea bags, add ½ cup of loose tea leaves directly to the cold water. ‘Brew’ as above, then strain the tea through a fine strainer or cheesecloth before drinking.

Green tea: Follow the directions as above, using up to 12 tea bags for a slightly stronger brew.

Mint tea: Add 1 cup of crushed mint leaves to the mixture before steeping.

Citrus tea: Sweeten the prepared tea with orange juice or lemonade. Or, garnish individual glasses with lemon, orange or lime slices.

Flavored tea: “Flavored tea mixtures can be especially good for making iced tea,” says Kathleen Curtis, co-owner of Village Roasters in Lakewood, Colo. “Apricot, mango, ginger and peach-flavored black teas are all popular for iced tea in the summertime, as well as fruity blends like strawberry-cherry and cinnamon orange spice. You can also experiment and combine several varieties of loose flavored teas to make your own custom mix.”