It's not the first time Trump has been seen drinking strangely.
In November, he picked up a bottle of Fiji water in both hands and sipped it awkwardly during a press conference at the White House.
And earlier this month, speculation went wild after Trump began slurring through part of his speech announcing changes to America's Israel policy.
He finished his remarks by saying "God bless the United Shhtates. Thank you very much-sh."
Conspiracy theorists on Twitter launched into high gear, including Democratic partisans who speculated about every possible cause from a mini-stroke to cocaine use.
TV host Joe Scarborough also weighed in, saying 'people close to him during the campaign told me [he] had early stages of dementia'.
A White House spokesman insisted the president merely had a case of "dry mouth," telling the Los Angeles Times that "his throat was dry. There's nothing to it."
Asked if Trump had any related health concerns, Shah said: "I know what you're getting at. I'm saying there's nothing to it."
But brain doctor Dr Ford Vox - who has never examined Trump - believes the incident and other moments in his presidency, reveals that Trump has all the symptoms of pre dementia.
In a lengthy analysis for Stat News, he also pointed to times when Trump has contradicted himself, rambles in interviews, makes faces, and forgets to sign bills at bill-signing ceremonies as "worrisome symptoms of illness.
In an attempt to regain control of the runaway story, press secretary Sarah Huckabee Sanders announced that Trump will undergo a physical examination early next year, with the findings released to the public.
Now, Monday's speech has reignited the rumours over Trump's health.
Twitter was awash with conspiracy theories within minutes of the 70-year-old's speech in Washington, where he told the servicemen and women: "On January 20, 2017, I stood on the steps of the capital to herald the day the people became rulers of their nation again," - before pausing to take a sip of water.
