You've seen the Heat Change Mug before on USA Housewares...
But here's what it looks like Mint in the Box. This reveals it's a Just Funky item, and is at Game Stop for about 12 dollars in 2021. It's nice to see it confirmed at brick/mortar retail.
The mug starts off black with a GHZ palm/flowers & logo, but then with hot liquid it reveals blue sky & run/jump/spin Sonic sprites across the side. The box art is nice too, with good photos illustrating the mug action & the neoclassic running forward Sonic in a ring. The box seems good for display too. 12 for something with a change feature isn't bad. Keep in mind these things are never dish-washer safe.