doc.tom (10 May 14 - 06:07 AM) mentions a variant that may be nearer the original meaning. Also, the number of persons involved in the ritual seems to vary from singer to singer. The word "We" in the beginning suggests some human company: even if the bottle were considered a friend, it would not have participated in the finding.

The following main points can be considered well-established: The narrator has no credit, which means social and financial problems. S/he needs to drive the resulting sorrows away. To achieve this, s/he and others designed a ritual ("act") which involves a bottle. To be sure, bottle-whistling can be great fun, but it takes more than one bottle. Spin-the-bottle is not such a thrilling pastime in the long run. Thus, it stands to reason that the trick involves drinking alcoholic beverages. The feeling of sorrow is driven away, but its causes are not - probably worsened. Priding oneself with disregarding these consequences (temporarily) is a fixed topos of drinking poetry since ancient times, not meant to be taken literally as a recommendation for a permanent way of life.