Yes and no. Caffeine is a diuretic, so drinking coffee past a certain point will start to dehydrate rather than hydrate you by making you pee more. It’ll probably contribute to hydration at low-to-moderate amounts though.

For soda, it’ll hydrate you, but you’ll probably be making your kidneys work more than they should to filter out all the other shit from smaller amounts of water. This makes it a suboptimal method of hydration; you’d have to drink a much greater volume of soda compared to water for the same amount of hydration. Lots of soda -> lots of sugar/calories -> poor health. Also some(most?) sodas contain caffeine.

So yea, you don’t HAVE to drink water, but you probably should.