Linda, you said, "'m not an expert, so you should probably take this with a grain of salt."
But salt also dehydrates - we'd need to drink MORE water to compensate!
Coffee - depends on how much caffeine is in it, plus how much else. Hot chocolate - same story, especially if it's made on all milk.
As soon as you add milk, you're adding other things too which slow down transit time. So while there is SOME fluid benefit, you can't count it all.
Best thing you can do - listen to your body. If you drink 8 glasses of water and no other liquids, you know how often you're in the loo. If you swap some of the glasses of water for equivalent volumes of coffee, hot chocolate or other drinks, you will notice you're not in the loo so often. It will vary.
One last important point - adding salt, sugar or anything is going to make it harder to absorb the water. In some cases, drinking a highly sweetened drink can dehydrate you, like drinking seawater would do. This includes substances like Isomalt (an optical isomer of sucrose which the body simply can't recognise). It tastes like sugar because it IS - it's a mirror image molecule. But because your body can't use it, it keeps going through your GI tract. And because your body needs it to be dissolved, it pulls water through the gut with it. It's like the old science experiment with osmosis, using a hollowed out potato with salt in it, then the potato floating in a glass of water. The hollow in the potato will fill up with water which is trying to lower the salt concentration.
So if you eat or drink too much Isomalt, it is dehydrating and it comes out, with its accompanying water, you know where. NOT the bladder.
So just drink the water.