Kai Trump Takes Secret Service to Erewhon to Buy $21 Hailey Bieber Smoothie

Kai Trump was living her L.A. girlie fantasy this weekend -- rolling up to luxury L.A. grocery hotspot Erewhon with her Secret Service escorts in tow to grab some essentials ... and the internet’s got a seriously sour taste about it!

Donald Trump’s granddaughter documented the trip in a video originally titled "I Brought My Secret Service to Erewhon," later changing it to "I Tried the World’s Most Expensive Grocery Store" ... showing her scooping up pricey items -- including the famous $21 Hailey Bieber smoothie -- plus supplements and other high-end goodies.

Kai seemed to be having a blast too ... even checking out the store’s clothing merch and asking how much it cost -- not that it looked like the price tags were slowing her down.

Still, she cracked a joke at the checkout about going bankrupt paying for it all ... and the internet wasn’t amused. Critics quickly piled on, pointing out plenty of people can barely afford groceries right now -- while others fumed that taxpayer dollars were footing the bill for the Secret Service detail.