Systems and devices cool content of individual beverage containers without sacrificing portability and cooling performance, and/or maintaining beverage containers cold. Exemplary implementations provide container having enclosed vertical double-wall structure with integral horizontal base defining interior space within enclosed vertical double-wall structure, or having wall structure formed from sheet of flexible material folded to form base and sealed along opposite sides of sheet to define interior space within wall structure and also having interior pocket formed by interior wall attached to interior surface wall structure. Interior space within wall structure is capable of accommodating at least one beverage container. Cooling material is sealed inside the double-wall structure, or removably placed inside interior pocket, to cool and/or maintain cold content of beverage container placed in interior space of container. Method includes providing container including wall structure accommodating cooling material and removably placing cooling material said structure.