A collapsible canteen having deposited therein a charge of water-soluble flavor crystals such that when the canteen is erected and water is poured therein, the crystals are then dissolved to produce, in situ, a soft drink. The canteen includes square top and bottom walls, the top wall having a projecting neck to receive a removable cap. Also included are a first pair of opposing side walls that are inwardly foldable in half whereby when the canteen is collapsed, the folded in first side walls are then sandwiched between the top and bottom walls, and a second pair of opposing side walls that are outwardly foldable in half and are each provided with a triangular gusset that is joined to a side wall in the first pair of side walls, whereby when the canteen is collapsed, the gussets are then folded into the folded out second pair of side walls to define a pair of outstretched wings, the wings being then folded under the bottom wall to create a square-shaped pack.