Fermented drinks are all the rage, turning up in health food stores and trendy supermarkets. Some, like kombucha and kefir, come with all sorts of health claims. Others, like naturally fermented sodas, are simply supposed to taste good. But these fermented drinks can be pricey ($20 for a bottle of coconut water kefir), and some of them taste more funky than fabulous.

So what’s the big draw, and are the benefits worth the price and effort? Here’s the scoop on five popular fermented beverages, including what to know about making them at home.

Kombucha

Aficionados call this slightly carbonated, sweet-yet-sour drink the “elixir of life.” Kombucha is made by fermenting sweetened black tea with a pancake-like colony of yeasts and bacteria often referred to as the "Kombucha mushroom" or as “SCOBY,” short for “symbiotic culture of bacteria and yeast.”

What can it do for you? That’s not exactly clear. Kombucha samples analyzed by researchers from Ireland’s University College Cork contained several types of beneficial Lactobacillus bacteria. This “friendly” family of “good bugs” is thought to promote good digestive health and lower the risk for digestion problems including traveler’s diarrhea and diarrhea caused by antibiotic use.

Related: 5 Common Antibiotic Mistakes

But in a 2014 review of kombucha research, scientists from India’s National Institute of Technology concluded that there’s “no evidence published to date on the biological activities of kombucha in human trials.” There’s no science to back claims that it might help prevent cancer or heart disease, bolster liver function or strengthen the immune system, according to the Mayo Clinic.

What to know about making it yourself:

Never use ceramic or lead crystal containers for kombucha. The Centers for Disease Control and Prevention warns that acids in fermenting kombucha can leach lead and other toxins from these materials.

Follow directions carefully. Makers of kombucha bacteria and yeast starters suggest you toss the batch and the “SCOBY” if you see any signs of mold growing on the SCOBY or in the fermenting tea. Homebrewed kombucha may also be contaminated with harmful bacteria, warn the American Cancer Society (ACS) and experts from Memorial Sloan-Kettering Cancer Center. The Mayo Clinic notes on its website that “Kombucha tea is often brewed in homes under nonsterile conditions, making contamination likely.”

Because of this risk, skip kombucha if you’re pregnant, breastfeeding or have a weakened immune system, according to the ACS.

Kefir

Kefir is similar to yogurt but is produced by fermenting milk with lactobacillus bacteria as well as yeast. The final product is tart, like buttermilk. Traditional kefir is fizzy and contains a little alcohol, which is usually removed from commercial versions sold in supermarkets and health food stores.

Related: 5 Tasty Ways to Eat More Yogurt

Health claims abound for this ancient, fermented dairy drink, touted online (and by tradition) as a beverage with the power to “help with” everything from herpes and allergies to tuberculosis, cancer and intestinal problems. According to the Academy of Nutrition and Dietetics, “evidence for these uses is largely anecdotal.”

While some of the health claims may be overblown, kefir does contain a wide variety of beneficial bacteria, including several strains of Lactobacillus, according to a Bulgarian Academy of Sciences analysis.

In a 2011 study published in the Journal of Medicinal Foods, kefir seemed to help people who were taking antibiotics to eradicate the stomach-ulcer-causing bacterium Helicobacter pylori. In the group that drank kefir twice a day, the infection was wiped out for 75 percent of the people. In the group that drank a non-kefir beverage, the infection was wiped out for just 50 percent of the people.

Kefir has another potential benefit: People with lactose intolerance seem to be able to digest it without discomfort, bloating or excess gassiness, according to a small Ohio State University study.

What to know about making it yourself:

Use only pasteurized milk and kefir grains (the term for the bacteria and yeast starter) from a reputable source, suggests the National Center for Home Food Processing.

Water kefir

Water kefir is fermented by mixing a solution of water, sugar and fruit with specialized kefir grains containing bacteria and yeast. It doesn’t have as many probiotic bacteria per serving as regular kefir, but it still has plenty. That’s good news if you don’t drink milk, can’t tolerate dairy or are looking for a lower-calorie kefir option. A 2011 study from Germany’s Munich Technical University found a surprisingly wide variety of bacteria including many beneficial Lactobacillus strains in homemade water kefir.

What to know about making it yourself:

Use water kefir grains, developed to break down sugars like sucrose and fructose, rather than regular kefir grains, which thrive on the natural sugar in milk. Water kefir can be sipped as a beverage in its own right; it tastes a little like lemonade. But it’s often added to fruit juice or coconut water to convert those drinks into kefir.

Related: Lemon Water: The (Somewhat) Bitter Truth

Coconut kefir

Made by fermenting coconut milk, this non-dairy kefir is a good option if you don’t “do” dairy. According to manufacturers’ labels, coconut kefir does contain live cultures of several strains of Lactobacillus bacteria.

But it has one big drawback: If you make it with the canned coconut milk used for cooking, as some recipes call for, it contains a whopping 445 calories and 45 grams of fat per cup according to U.S. Department of Agriculture nutrition information. Lower-calorie options use sweetened or unsweetened coconut milk beverages or coconut water, and these contain as little as 12 calories per serving.

Don’t believe everything you read about coconut water kefir’s purported health perks. Some are downright puzzling. One brand claims to do everything from balancing your emotions to “cleaning out” the body’s endocrine system (whatever that means) to making menstrual periods more “normal.”

In 2014, the Food and Drug Administration issued a warning about false marketing claims that coconut kefir could treat autism and digestive problems related to autism. “They have not been proven safe and effective for these advertised uses,” said the agency.

Related: Why Am I So Gassy?

What to know about making it yourself:

You can make your own by fermenting coconut milk with regular kefir grains or by adding coconut milk to water kefir (see above), according to one maker of kefir grains. To make coconut water kefir, start with water kefir grains. It’s smart to follow directions and safety precautions closely.

Related: Milk Alternatives: How Do They Stack Up?

Fermented fruit soda

Wildly popular online, where you’ll find recipes for homemade fruit sodas fermented with a do-it-yourself yeast starter, these naturally fizzy drinks add effervescence to your favorite juice. The calories are on par with commercial fruit sodas, but proponents say that they taste better. Fans also say these natural sodas give you the vitamins, minerals and phytochemicals you’d get from plain fruit juice, though you could also get that by mixing fruit juice with carbonated water. Fermenting with yeast also contributes B vitamins.

What to know about making it yourself:

Some recipes start with a “ginger bug” — sugar, water and grated fresh ginger, which may be left uncovered on a table or countertop to collect and feed wild yeast and bacteria. The “bug” is then added to fruit juice. Follow directions carefully; the fermenting juice can explode if gases build up in the bottle. Not ready to brew your own? You’ll find fermented sodas at supermarkets and health food stores.

Related: Can soda shorten your life?

Sari Harrar is an award-winning health, medicine and science journalist whose work appears in Dr. Oz The Good Life magazine, Good Housekeeping, O--Oprah Magazine, Organic Gardening and other publications.