Flavored water. Water with electrolytes. Tonic water. Sparkling water. Seltzer.

Grocery shelves are packed with so-called water options. But not every drink that bills itself as water is the real deal.

Many drinks labeled as water are loaded with sugar and empty calories. Even though these drinks have ‘water’ in their name, drinking them regularly may cause weight gain and may increase your risk of obesity.

And, that’s bad news because maintaining a healthy weight is one of the most important things you can do to curb your cancer risks.

So, how can you tell which water drinks are the real deal and which ones are no better than soda and sugary drinks?

Here’s what to look for — and what to avoid.

1. Check the calories

Real water has zero calories. Always check the packaging label to see if a so-called water beverage has calories.

If it does, check the serving size and do the math. Many bottled or canned drinks have two or more servings, which can add up to as many as 250 to 400 calories.

2. Watch out for sugar

Some so-called water drinks include sugar, fruit juice or other sweeteners. So, be sure to check the total carbohydrates and sugars on the nutrition label.

Your drink is only real water if the total carbohydrates and sugars are listed as 0.0 grams.

Over time, drinks with a lot of sugar and/or caffeine can dehydrate you, no matter how much water they have. And, that can cause headaches, dizziness and decreased blood pressure.

3. Don’t be fooled by added vitamins, minerals or fiber

It’s okay to occasionally drink a beverage with added vitamins, minerals or fiber. But beware: beverage companies often market these nutrients to trick you into thinking you’re getting something healthy — and to make you overlook the unhealthy parts of the drink, such as sugar.

Keep in mind that you should get your nutrients from fruits, vegetables, whole grains, healthy fats, and lean protein whenever possible — not from drinks.

4. Electrolytes aren’t usually necessary

Many drinks promise electrolytes and improved athletic performance. But in most cases, your body doesn’t need to replenish electrolytes unless you’re doing aerobic or outdoor activity for longer than 60 minutes. Regular water should provide the hydration you need.

5. Drink filtered tap water when possible

Whenever possible, opt for filtered tap water. Not only will you save money; you’ll also reduce your exposure to toxins like Bisphenol-A (BPA), which may get into water that’s sold or stored in plastic bottles. Play it safe by keeping your filtered tap water in a glass or stainless steel BPA- and phthalate-free container.

6. Drink 8 glasses of water every day

Try to drink at least 64 ounces — or 8 glasses — of real water each day. Your body needs this much water to stay hydrated and work efficiently. And, it helps you feel full longer so that you eat less and maintain a healthy weight. Research suggests that replacing sugary drinks with water may even help you shed a few pounds.

Don’t like water? Cut up berries or an orange, lime or lemon and put them into your water for extra flavor. Added bonus: you’ll get some disease-fighting vitamins and antioxidants.

Remember, it’s okay to get a little sugar from drinks every now and then. But real water should be your main go-to drink.

Mary Ellen Herndon is a dietitian at The University of Texas MD Anderson Cancer Center and nutrition reviewer for MD Anderson’s Focused on Health newsletter.