To make beer batter, combine flour, baking powder and salt in a mixing bowl. Then pour in 1/2 cup of beer and whisk the batter until smooth. After pour in the rest of 1/2 cup of beer.
Whisk until everything is combined and there are no lumps.
To make sweet and sour chicken, using a wok or a frying pan, fill it up halfway with avocado oil or any oil of your choice. Preheat the oil over medium/high heat. Working in batches, toss each chicken piece in 1/2 cup flour.