The amount of water bottles you need to drink per day to equal the 8 cups of water per day or 8 glasses of water per day would be 4 bottles of water.
That would be 4 bottles of the 16 ounce water bottles you would need to drink each day to equal out the 8 cups of water or 8 glasses of water per day.
Drinking 8 glasses of water per day is healthy for you but you don't have to drink 8 glasses or 8 cups of water everyday to stay healthy.
As long as you're drinking at least a few glasses of water or a few bottles of water and drinking other drinks such as orange juice, tea, coffee etc you will still be hydrated enough.
However water is one of the best and healthiest drink you can drink to help keep your bladder and kidneys healthy and flushed out.