Why it happens
Meringue is a foam of whisked egg white and sugar. If the sugar isn't fully dissolved, or the meringue is overbaked, sugar syrup can be pushed out and form sticky beads on the surface. Liquid under a pie topping is usually caused by the bottom of the meringue staying undercooked, often because it was spread onto a cold filling. Humid weather also makes meringue absorb moisture and weep.