Our bands require a hot nutritionally balanced meal for each member plus one crew member.  The group doesn’t need anything fancy and it doesn’t need to be what your guests are having.  Venues will often have some type of vendor meal available.   The group may request a few vegetarian options if available.  Water, juice and soda should also be made available to the band if possible.   That is always appreciated.  It is also recommended that you consider a “break area” for performers.  This may be a designated “green room”, table or unobtrusive area away from guests.