Real candles.
I made an Advent wreath about 60 years ago of plaster of paris with small pine cones and seed pods with candles. My mom could never bring herself to light them lest it destroy my wreath. 10 years ago after my mom passed away, my wife found it and it crumbled in her hands without the candles ever being lit.
Not sure candles are even "in" anymore. My oldest Granddaughter had her first advent wreath last Christmas and it chocolates on it. And someone here on the DIS was looking for the best place to buy an advent wreath with mini bottles of wine.