sometimes when i hit the gas or brake hard i hear a noise like water in a bottle moving around anyone ever hear or know what this is?

 

A less than full gas tank makes that noise in some cars. Other than that, I dunno what to tell you...

 

maybe there is a water bottle in the back seat that u dont know...?lol

 

It's not uncommon. I have read a thread or two regarding that very thing. I hear it in mine occasionally. It sounds like water behind the dash. I believe it has something to do with the heater core. I can't remember what I was searching for when I ran across the threads. But there is info on CL regarding what you're asking.

 

It could be a clogged heater core, but more often its caused by air bubble in the coolant system. Bleed your coolant system and fill it to spec, and it should go away.

 

Yep, for the OP, do a search for "low coolant".

It's more of a gravel sound

 

Happened to my Avalon...
it was literally water collecting between the door panels

 

I think of trickling water sound when if first happened to me