Wa'alaikum assalam sis! Okay so this is super common, jangan worry lah, banyak baby fully breastfed reject botol susu especially dari babysitter sebab diorang detect mummy's smell dia absent! One trick a few of us tried is warm up the formula milk, sometimes baby ni prefer hangat-hangat macam direct dari breast; also try biar babysitter yg feed, bukan mummy, because baby tau mummy ada so dia cari breast je. Another thing, some babies prefer cup training dulu daripada botol (beli sippy cup yg easy flow), so mungkin boleh skip botol stage altogether kalo babysitter boleh handle that. Since he drinks water from bottle fine, susu boleh try campur sikit dengan air or slowly transition, tapi honestly sis, if he's rejecting multiple formulas and botol types, definitely worth checking with your pediatrician whether ada sensory issue or just stubborn baby behavior, they can guide better and sometimes boleh suggest formula yg closer to breast milk taste. Hang in there mama, 6 months on pure breastfed pon dah amazing!