Just as you often see plastic dishes with mess kits, you will also tend to see silicone cups. A question that got brought up a few times was whether or not these types of cups could handle hot liquids. Well, if you know anything about silicone (which is fine if you do not as it is not like the average person will be knowledgeable of its properties) than you should be able to answer this question without even testing it.
Generally, silicone is meant to be heat-resistant. As the polymer is used in sealants, adhesives, and for thermal insulation, it is designed to withstand heat. So, yes, with silicone cups, you are perfectly safe to drink coffee, hot chocolate, or any other hot liquid that you would like to place inside.