In a medium bowl, whisk together the flour, garlic powder, onion powder, paprika, black pepper, red pepper flakes (if using), and salt. Slowly whisk in the beer or water until the batter is smooth.
In a separate bowl, beat the eggs.
Place the panko bread crumbs or crushed crackers in a shallow dish.
Heat oil in a large skillet over medium heat.
Dip each pickle slice into the batter to coat completely. Shake off any excess batter and then dip into the egg mixture and then into the panko bread crumbs or crushed crackers to coat completely.
Carefully place each pickle slice into the hot oil and fry for 2-3 minutes on each side until golden brown. Remove from oil and place on paper towels to drain.