I claim the ornamental design for a combined baby bottle nipple and bottle cap for fitting on water bottles, as shown and described.
FIG. 1 is a perspective view of a combined baby bottle nipple and bottle cap for fitting on water bottles, showing my new design, the broken line showing of the bottle being for illustrative purposes only and forming no part of the claimed design;
FIG. 2 is a top view of the combined baby bottle nipple and bottle cap for fitting on water bottles of FIG. 1;
FIG. 3 is a side elevational view of the combined baby bottle nipple and bottle cap for fitting on water bottles of FIG. 1; and,
FIG. 4 is a bottom view of the combined baby bottle nipple and bottle cap for fitting on water bottles of FIG. 1.