WINSTON-SALEM, N.C. - Krispy Kreme is offering Americans a sweet incentive to get a COVID-19 vaccine by giving a free doughnut to anyone who shows proof of vaccination — and inoculated customers can keep going back every single day for the rest of the year.The company announced Monday that anyone who shows a valid COVID-19 vaccination card will get a free Original Glazed doughnut at participating Krispy Kreme locations nationwide for the remainder of 2021.Customers must bring in their own COVID-19 Vaccination Record Card to redeem the offer, and they can go back for one free doughnut every single day — no purchase required, the company says.