It is widely known that soda, beer and coffee are bad for your teeth.
Bottled water, however, seems harmless.
But dentists warn that is not always the case.
Some of the most popular brands of bottled waters have dangerous pH levels and lack essential fluoride, which can cause cavities.
However, it is impossible to know from the label which ones are the safest - so we tested the pH levels of nine top brands to see which ones were the best and worst.
The pH level can range from zero to 14. On that scale, seven is neutral, anything under that is acidic and anything higher is alkaline.
Our investigation found that samples of four of nine popular bottled water brands were very acidic. The brands - Smartwater, Dasani, Aquafina and Voss - had a pH level of 4
We tested nine bottled water brands to see their pH levels. Brands with pH levels closer to zero are more acidic and can erode your tooth enamel. Brands with pH levels between seven and 14 are alkaline.Smartwater: 4 Aquafina: 4 Voss: 4 Dasani: 4 Poland Spring: 7 Volvic: 7.5 Fiji: 8 Essentia: 8 Evian: 8.5
Drinking acidic water will harm your teeth, warns Dr Eunjung Jo of Astor Smile Dental.
'Our enamel starts to erode at a pH level of 5.5 so it's best to avoid any drinks with a pH that is lower than 5.5.'
Dr Jo also said that the damage done to your teeth increases proportionately with the time you spend sipping on a drink so spending three hours drinking a coffee is more harmful than downing it in 30 minutes.
'The longer you sip and they stay in your mouth, [the] damage is bigger,' she said.
She added that bottled water is not worse for your teeth than sodas, beer or coffee and she thinks Fiji water is the best for your teeth while Dasani, Voss and Smartwater are the worst.
The lack of fluoride - a healthy ion that is good for tooth enamel - in bottled water can also be harmful.
Tap water is regulated by the government, which makes sure it has accurate fluoride levels, but bottled water often lacks proper amounts of it.
Dr Tema Starkman of High Line Dentistry said it is important to make sure you are always consuming fluoride.
She said that this is especially important for children between the ages of zero and five whose teeth are still developing.
If these children do not receive proper fluoride levels they can develop hypo-fluorosis, a condition that can leave white spots on their teeth, she said.
'If they are not