Crush the vanilla wafers into fine crumbs. Use a food processor for an even crumb, or seal in a zip-top bag and roll with a rolling pin until sand-like.

In a large bowl, stir together wafer crumbs, chopped pecans, 1 cup powdered sugar, 1/4 cup cocoa powder, espresso powder (if using), and salt until evenly combined.

Add the rum, corn syrup, and vanilla. Stir with a spatula until the mixture looks uniformly moistened and starts to clump when pressed. If it seems dry, add 1 to 2 teaspoons more rum or water.

Cover and chill the mixture for 20 to 30 minutes until it firms slightly and holds together when scooped.

Set up shallow bowls with coatings: shredded coconut, sprinkles, additional powdered sugar, and additional cocoa powder.

Scoop about 1 tablespoon of mixture per ball and roll between your palms into 1-inch balls. If the mixture sticks, lightly dust your hands with powdered sugar.

Roll each ball in your chosen coating, pressing gently so it adheres. Place on a parchment-lined tray.

For the best flavor, rest the rum balls in an airtight container for 24 hours at cool room temperature or in the refrigerator before serving. Serve chilled or at room temperature.