The answer depends on the flavored malt beverage, but spiked seltzers are typically keto-friendly, since they have a low amount of carbohydrates per serving. Look at the label and aim for a drink with 2-5 grams of carbohydrates if you want a drink that's more keto-friendly. Most keto diets recommend staying under 20-50 grams of carbohydrates each day, so any beverage can fit your diet if you account for it with the other foods or drinks you consume for the rest of the day.