A question about water ad a bottle

My water bottle sometimes times farts. What do I mean by this?
It makes a "pffft" sound from time to time. I don't know why. It's plain water, with no gas, no bublles, nothing.
What kind of phisical thing is happening here to make the water bottle make this gas like sounds?

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RandomForest ·

You mean when you first open it?

Alfarrobas · 36-40, M

@RandomForest Oh, no. It's a metal bottle I fill up with water and use. Not a new one

RandomForest ·

@Alfarrobas Then I have no idea. For plastic bottles to use less plastic they pressurize the water so the plastic bottles don't collapse during shipping but here I am not sure.

Alfarrobas · 36-40, M

@RandomForest thanks. That i didnt knew. ☺️