I can imagine price stickers would update daily, and individual users would get personalized discounts on their app.
App-less buyers would pay the baseline price in the sticker, app users would pay less. Like existing loyalty card programs, but with more data collection
Not necessarily April fools jokes, but the Gboard team has been designing and making silly keyboards (and publishing the schematics)

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Sharyn Alfonsi's Inside CECOT for 60 Minutes, which was censored by Bari Weiss, as it appeared on Canada's Global TV app.