  A spanner is a sparse subgraph of a given graph $G$ which preserves
distances, measured w.r.t.\ some distance metric, up to a multiplicative
stretch factor. This paper addresses the problem of constructing graph spanners
w.r.t.\ the group Steiner metric, which generalizes the recently introduced
beer distance metric. In such a metric we are given a collection of groups of
required vertices, and we measure the distance between two vertices as the
length of the shortest path between them that traverses at least one required
vertex from each group.
  We discuss the relation between group Steiner spanners and classic spanners
and we show that they exhibit strong ties with sourcewise spanners w.r.t.\ the
shortest path metric. Nevertheless, group Steiner spanners capture several
interesting scenarios that are not encompassed by existing spanners. This
happens, e.g., for the singleton case, in which each group consists of a single
required vertex, thus modeling the setting in which routes need to traverse
certain points of interests (in any order).
  We provide several constructions of group Steiner spanners for both the
all-pairs and single-source case, which exhibit various size-stretch
trade-offs. Notably, we provide spanners with almost-optimal trade-offs for the
singleton case. Moreover, some of our spanners also yield novel trade-offs for
classical sourcewise spanners.
  Finally, we also investigate the query times that can be achieved when our
spanners are turned into group Steiner distance oracles with the same size,
stretch, and building time.
