The bottom should measure 6 inches across and it will take 5-1/2 cups water to fill it up to the top. Prepare the souffle dish: Cut a piece of nonstick aluminum foil 25 inches long; fold it in half lengthwise with the nonstick side out. Wrap it around dish with the folded edge up. Press the two ends together; fold twice to make the foil fit tightly around the dish. The collar will rise about 3 inches above top of dish.
Place gelatin in small heatproof bowl. Add boiling water and stir until gelatin is completely dissolved, 2 to 3 minutes. Let cool 10 minutes.
Meanwhile, place berries, sugar, juice and tequila in food processor and process until berries are pureed. Pour into large bowl.
Stir dissolved gelatin into strawberry mixture until well combined. Using wire whisk, gently fold in whipped topping until no white streaks remain, 2 minutes. Pour into prepared dish, smoothing top. Refrigerate until set, 6 hours or overnight.
To serve, carefully remove collar. Gently press sugar onto exposed sides of mousse and garnish with lime and strawberries, if desired.
Makes 8 servings.