Mix sugar and 1/2 teaspoon of the OLD BAY in small plate. Wet outside rims of 2 beverage glasses with water. Dip glasses into OLD BAY mixture to coat. Set aside.
Mix lemonade, lime juice and remaining 1/4 teaspoon OLD BAY in large liquid measuring cup or small pitcher. Slowly stir in seltzer.
To serve, refrigerate lemonade until chilled or pour into ice-filled rimmed glasses.