Print projects have an advantage digital posts don't: someone has to physically turn the card or tag to read it, which makes the flip itself part of the interaction instead of just a visual trick. A few ways it works particularly well on paper.
For a topsy-turvy or "world turned upside down" themed party, printing the invitation details in flipped text and pairing it with a line like "flip this card to find out where" turns the invite into a tiny puzzle before the party even starts. It works especially well for kids' parties, since the physical act of turning the card over is itself part of the fun.
A gift tag with a normal "To/From" line on one side and a flipped message on the other reads as a small surprise once the recipient notices it's not printed backward by accident. Keep the flipped line short — three to five words — since gift tags are small and dense flipped text is harder to read at a glance than at full size on a screen.
Not every font used in design software includes glyphs for the specific Unicode characters flipped text relies on, so it's worth checking your printed proof before running a full batch — if a character shows as a blank box on your screen, switch to a more complete system font (like a standard Arial, Helvetica, or Noto family) rather than a decorative one, since those tend to have the widest character support.