One of the main tips when starting as a noob on the beach is to find a water pump in a town or village and drink until you can’t drink anymore. This will mean you can easily get away from the coast or do some serious looting without having to worry about your water level for a while.
If you find a water bottle in dayz or a canteen of water I would not drink it straight away as there is a chance you could get a nasty disease, make sure you pour out any water that comes with it and refill at a pump. Receptacles can be filled and water can be drunk from ponds, lakes, dams and extracted from water pumps.
There is no need to disinfect bottles or canteens, disinfecting bottles does nothing. You can use chlorine tablets to get rid of the chance of contracting cholera from bottles of water that you have found containing water that is potentially infected. There is a chance of getting it from water pump too so using a chlorine tablet or taking a multivitamin pill before drinking is a great way to protect yourself.
Another nice tip is to use some larger vessels like jerrycans or cooking pots to drink from, you can use 1 chlorine tablet on it but get to drink a whole lot more water. Drinking rainwater from barrels is 100% safe as well unless you pour contaminated water then it ruins the entire barrel and you can’t use chlorine tablets on it.