Has anybody tried this?!😅😅 I’m DESPERATE

So my son is 9 months.... 9 months and refuses anything except the boob. I’ve tried breast milk in sippy cups, 4 different types of bottles/nipples, open cups, syringes, everything... EVERY THING. He loves drinking water from his sippy cup but the second I put breast milk in it he pushes it away. He pushes everything away... I’ve left the house for 8 hours during the day before to have dad feed him and he didn’t have any success.

My question is, has anybody had the same problem and used formula in a bottle instead? And then slowly mix breast milk in? Idk what else to do, and I’m going to work next week.