Lightly spray a 9×13-inch pan with nonstick spray and set aside.
In a large pot over low heat, melt the butter and dissolve the salt.
Add 14 ounces of the mini marshmallows and stir until melted and smooth.
Whisk in the apple cider drink mix, and vanilla until fully dissolved.
Remove from the heat and fold in the Rice Krispies cereal until evenly coated.
Fold in the remaining 2 ounces of mini marshmallows.
Transfer the mixture to the prepared pan and gently press into an even layer. Avoid packing the treats too firmly.
Let cool for about 1 hour before cutting into 16 squares.