According to the American Cancer Society, "some fluorides naturally in soil, air, or water, although the levels of fluoride can vary widely. Just about all water has some fluoride." Additionally, fluoride is "supplied to about 3 out of 4 Americans." The American Cancer Society does note that states and local areas are the ones who decided whether or not to add fluoride to drinking water. However, consumers are protected by regulations, such as "The US Environmental Protection Agency (EPA) has set a drinking water standard, which is the maximum amount of fluoride allowable in public drinking water systems, of 4.0 mg/L." For bottle water specifically, water with "no fluoride added, the maximum fluoride level allowed varies, but can be up to 2.4 mg/L (in places with colder annual average air temperatures)." For water with fluoride added, "the maximum allowed is 0.7 mg/L, which is in line with the PHS recommendation." So while fluoride is in most bottles of water, consumers are protected by regulation.
Source: https://www.cancer.org/healthy/cancer-causes/chemicals/water-fluoridation-and-cancer-risk.html