HELP PLEASE CALLING ALL MOTHERS

I’m babysitting a 3 month old boy. He is breastfed. The parents said he takes a bottle “OK”. He was nursed at 4 by mom before she left and it’s currently 815 and he’s eaten maybe 2 oz total because he’s screaming and refusing to take the bottle. Hes burped and farted multiple times. He’s changed and dry. He just will not take this bottle and I feel bad. He’s starting to fall asleep should I just let him? Is he gonna be okay with only 2 oz ? What can I do to get him to drink the bottle. He’s rooting like he wants a nipple but won’t take the bottle. Please help