Can I bring an empty Hydroflask or Nalgene water bottle into the park and fill inside the park?

Yes I was there 2 days ago and we took empty yeti bottles to be filled up in park

Yes water bottles are allowed. They do give you unlimited complimentary water. I have season passes and have been going almost everyday. I took my hydroflask and my kids did also. No one said anything.

Yes!! They have water bottle filling stations

Yes

Only with water

I brought cups there. Can refill every 15 min. The whole season

Yes you can plus they have free water station all around