(TrendHunter.com) These new Shake Shack holiday shakes are being launched by the brand in celebration of the upcoming 2021 holiday season that will provide patrons with an unexpected way to enjoy some festive flavor.... (TrendHunter.com) These new Shake Shack holiday shakes are being launched by the brand in celebration of the upcoming 2021 holiday season that will provide patrons with an unexpected way to enjoy some festive flavor....