Cutting out most sink cabinet back panel to access utilities
If it is only 1/8&quot; and there are some structural pieces (typically near the top and bottom) across the back then the panel is not structural and can be removed. In fact, many times the back panel won't even be installed on a sink cabinet. However, if there are no other structural cross pieces on the back then, depending on how well the cabinet is built, how it is attached to the wall, type of countertop, etc., the panel may be important in keeping the cabinet straight.
The only concern I would have is the increased possibility of unwanted cold air or critters coming in, particularly if this is against an outer wall.