Step 1

Whisk mayonnaise, Sriracha, lemon juice, and garlic in a small bowl; season with salt.

Step 2

Pour grapeseed oil into a medium heavy saucepan; fit with deep-fry thermometer. Heat over medium heat until thermometer registers 350°.

Step 3

Whisk flour, cornstarch, and baking powder in a medium bowl. Whisk in 3/4 cup seltzer water. Whisk in more seltzer, if needed, until batter is the consistency of heavy cream.

Step 4

Working in batches, coat pickle slices with batter, letting excess drip off, and add to oil one by one (to prevent them from sticking to one another). Fry, turning halfway through, until golden brown and crisp on both sides, about 3 minutes per batch.

Step 5

Using a slotted spoon, transfer to a paper towel-lined plate. Serve with spicy mayo.