Preheat the oven to 225F. Line two sheet pans with parchment paper. 

Add the egg whites to the bowl of a stand mixer. Beat on medium-high speed (speed 8 on a Kitchen aid), adding the sugar gradually over the course of 3-5 minutes. Beat until soft peaks form. 

Once soft peaks have formed, add the vanilla powder, gel food coloring (if using), and the vinegar. Continue to beat the egg whites on medium-high speed until stiff peaks form. 

Once the egg whites have become stiff peaks, transfer the mixture to a piping bag. Pipe 1-inch heart shapes about 2 inches apart on the parchment-lined baking sheets. Decorate with sprinkles, if desired. 

Bake for one hour, then turn off the oven and leave the oven door open to allow the meringues to cool slowly to room temperature-- about 2 hours.

Once the meringues have cooled fully, transfer them to an airtight container and store at room temperature for up to three days.