Carry pepper spray and use it. You'll be doing the dog a favor. If the dog feels encouraged to keep chasing, eventually it'll be struck by a car and maimed or killed. Or eventually it'll attack a cyclist, jogger or kid and seriously injure them. I've used it once and it worked immediately.
I carry the gel stream stuff that doesn't splatter back toward me, unless there's a stiff headwind, in which case I won't use it.
I've never seen a water bottle accomplish anything more than encouraging a chasing dog to think it's a game. Some dogs like to play in high pressure water streams in the garden, so they sure won't be discourage by a squirt from a water bottle. The only critter I've ever seen disturbed by a water bottle squirt was a young rattlesnake I chased off the highway last year. Won't work on copperheads since they like water.
And I don't try to outrun dogs. That's just asking for trouble. I slow down, stop and get off if necessary and put the bike between me and the dog, and watch for continued aggression. Most dogs will lose interest and trot home. But if the dog persists in being aggressive, Precious is gonna get the pepper spray hose.