A video shows Jonathan White, 25, asking a female bartender for a glass of tap water in the Clock Hotel pub to swallow his medication.
Cabin crew White, out with his pal Shaun, claims the blonde barmaid told him to pay £1($1.27) for the water or leave the pub.
In the video he repeatedly asks if she is refusing him water "even though I've got a medical condition" (depression), at the pub in Hebburn, North Tyneside, at 9:45pm on June 15.
The barmaid can be heard saying, "If you've got a medical condition, you've gotta go home."
After White insists that he needs water to take his antidepressants, she then says "you can tape us as much as you like" before appearing to swipe at his phone.
Jonathan was "shocked and upset, and already vulnerable" - and immediately reported the incident to police.
Northumbria Police has asked anyone with information to get in touch.
He said, "I was anxious and scared. She wasn't supposed to be charging us anyway for tap water. When I raised this with her, she made me feel really vulnerable.
"I was made to feel stupid and insecure around her. Shaun thought she was nasty. I even told her that I'd bought two pints, and then she hit me.
"I couldn't see why she wouldn't just pour me a glass of water for my medication."
Jonathan said he was surprised he was being charged £1($1.27) for tap water, and claims that he brought only two pints' worth of cash with him.
He said he doesn't own a contactless debit card, and his American Express card wasn't working.
A spokesperson for Northumbria Police said: "Shortly before 10pm, June 15, police received a report of an assault at the Clock Hotel, Hebburn.
"Enquiries are ongoing and anyone with any information is asked to contact police by calling 101 and quoting reference number 1217 15/06/19."
The Clock Hotel has been contacted for comment.