I am not sure that someone can be considered a water bottle expert exactly. But if they can, I am pretty sure I have a Ph.D. in water bottles. My husband calls my collection excessive; I call it thorough. You need different water bottles for different things even in cycling. Let’s talk about when you need what.
When you are riding short
You just need something that fits inside your water bottle cage on your bike. Unfortunately, water bottles and water bottle cages are not universal, so you will need to find one that fits yours. But don’t feel like the more expensive the better. Honestly the water bottles you get in race goody bags generally work great for this. You may want to up the ante and get an insulated water bottle if you live in a hot climate or like your drink ice cold like I do. Look for an easy open spout that you can open with your mouth.