Brown showed off her face mist and even claimed to apply her facial scrub, but fans were left confused as it appeared she wasn't actually applying anything on her face, and just rubbing it without any product on.
Fans also pointed out that Brown's eye makeup remains intact throughout the tutorial.
"I can't believe she's literally just dry rubbing her hands together and rubbing her face. Like is this a prank?" one fan wrote on Reddit, as cited by Page Six.
Added user another, "I don't ever believe that celebs are ever selling us the skin care routine they actually use. But I still expect them to be willing to use it at least once! If you're not willing to even put it on your face to make a sale, why should anyone else use it for real?"
A third one commented, "WTH was this. Do brands really think we don't have eyes, like for real?"
However some came to her defense, writing 'For the love of god can we stop making fun of Millie Bobby Brown she is a CHILD (plus 100000x less cringy than any of us were at that age, come off it)'.
The clip was soon deleted from the photo-sharing application after fans began speculating the actor was just pretending to use her products.
The actor isn't the first star to be called out for promoting her beauty line in a misleading manner. The American reality star and makeup mogul Kylie Jenner, who recently launched her skincare range, was criticised by people for her skincare routine.
The 21-year-old star received flak for using the foaming face wash and still ending up with a lot of makeup on her face. She also faced backlash for using a filter while washing her face using products from her skincare range.
Last year, Shay Mitchell made headlines for a Snapchat video promoting Biore's makeup remover. In the clip, she faked to remove her eye shadow with a cotton pad, but her makeup remained perfectly intact.