It depends a bit on the capacity of the bottle, right?
If you are used to filling bottled water in liter bottles, the answer is 3785 bottles per bottle. Gallon. If you prefer 1/2 liter bottles, the answer would be 7571 bottles per. Gallon. Some brave people pack their stuff in 355 ml bottles. In this case, there would be 10,663 bottles each. Gallon.
On the other hand, if you can still find a bottle of beverage marketed in imperial units, there are 16 half-bottles or 8 bottles in a gallon and then 4-liter bottles or 2-bottles. half a gallon in a gallon.