(Warmest)
I would Say the answer is 2 Layers of foil around the cup Because we Use Foil for everyday cooking to Keep the heat from leaving the inside , Like a insulator .
Then I would say 2 Socks on the cup Because Its like a insulator because if you think of like feet at night time when its cold it warms them up but I dont think it would be as good as Foil.
Then I would say the Cup within The Cup because It would be like double the Withstanding of the heat.
Then I would say The Ziplock Bag because it doesnt really keep it warm for long but I feel like it would keep it warmer longer then it just sitting in a cup itself .
Then Finally The Cup Alone.
(Coldest)
I hope I helped you out in some way or atleast tried to
-Dante