Preheat the oven to 300°F.
In a medium-size bowl, whisk together the beer, sriracha, liquid smoke, mustard, salt, and pepper.
Add the flour and whisk until smooth. The mixture should coat the onion ring well without dripping off.
Add 1 tablespoon flour or beer if needed.
Line a baking sheet with paper towels.
Heat 1-inch canola oil in a heavy-bottomed pan over medium-high heat.
Working in batches, dip the onion rings into the mixture, then slide into the hot oil. The oil should sizzle but not ripple. Adjust the heat if necessary. Be careful not to crowd the pan or the oil temperature will drop.
Cook the onion rings for 1 to 2 minutes, or until golden brown.
Drain on the baking sheet.
Keep warm in the oven until all are cooked.
Repeat with the remaining onion rings.