Possible Clues:

• Big name in slush
• Drink often served with a spoon-straw
• Frozen pop brand
• Drink commonly served with a spoon-straw
• Drink brand with a polar bear symbol
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• "America's FLAVORite Frozen Beverage since 1967"
• 'America's FLAVORite Frozen Beverage since 1967'
• Cold drink at Burger King
• Brain-freezing brand