Push each candy bar onto a skewer or popsicle stick; refrigerate for at least 2 hours or overnight.
Whisk the flour and baking soda in a medium bowl. Whisk in the seltzer to make a smooth batter (about the consistency of pancake batter). Heat 4 to 6 inches of vegetable oil in a deep pot until a deep-fry thermometer registers 330 degrees.
Hold the Snickers by the skewer and dip into the batter, turning to coat. Carefully place the Snickers in the hot oil (skewers and all); fry, turning as needed, until crisp, 1 1/2 to 2 minutes. Use tongs to remove each bar by the stick; drain on paper towels or a rack and serve warm.