A common tradition among hikers and backpackers is to carry a trail cup. This is a personal cup or mug, usually metal, that a hiker carries. An early version was know as the Sierra Cup. It has a wire handle and can be hung on the outside of a pack. The cup can be used for drinking, sharing a drink from a bottle, scooping water from a stream (before purifying or boiling), or heating over a fire or stove. Newer trail cups are more likely to be mugs, they hold more and a steadier over a fire.
Traditional Sierra Cup
Some cups have folding handles, some are ultra-light weight, some are the old fashioned blue enamel, much like might be found on a cowboy chuck wagon with a matching coffee pot. If packed inside a pack, instead of being hung on the outside, they are a useful way to pack small items, such as matches or even spare socks.
 Stainless steel folding handle mug |  Ultra-light weight titanium mug |  Old-fashioned enameled steel mug |
The enameled steel, while heavier, is inexpensive and easily found. Wal-Mart has them in their sporting goods department. They are a recommended addition to an Explorer's backpack. Plastic mugs are lighter, but cannot be used on a fire or stove. Insulated mugs likewise cannot be used on a fire or stove since the insulation defeats the effort to heat the contents. Either of these are options, but are somewhat less versatile.