Combine flour and beer in a large bowl, blending thoroughly.
Cover and allow batter to sit at room temperature for at least 3 hours.
Afterwards gently stir in the sugar and salt.
Cut onions into one-fourth inch or larger (depending upon preference) slices.
Separate slices into rings. Heat shorting to 375 degrees F. Dry sliced rings and roll in flour.
Then dip onion rings into batter and fry until delicate golden brown.
The batter can be made thicker by adding more flour or thinner by adding more beer.