U.S. patent application 20170325607 (applicant Pacific Market International LLC, Seattle, Wash.):
"A beverage container provided with a thermal regulation member having a sidewall extending through a beverage cavity of a container main body. The thermal regulation member contains an energy storage material that receives, stores, and transmits heat energy to and from a beverage in the beverage cavity to regulate its temperature. The energy storage material may initially absorb energy from a heated beverage having a temperature too hot for drinking, then transfers heat energy back into the beverage as it cools, keeping it within a comfortable temperature range for an extended period of time. The thermal regulation member may be selectively attachable to a stopper assembly that seals an upper opening of the beverage cavity. Alternatively, laterally extending attachment members may attach the thermal regulation member directly to a wall of the beverage cavity. ... The energy storage material  may be a phase change material that undergoes phase changes within and around temperature ranges that are comfortable for human consumption of beverages."