re: I have a 3 month old baby that refuses to sleep when he's tired

White noise machine or just YouTube it on your phone. Rock him. We started using a sleep sack at some point but when he was younger we used a swaddle thing that worked well, it wraps them up tight - I don't remember how many months old when we made the switch, maybe 4 or 5. It also helped with mine if you gave him a few sips of a bottle. He wouldn't finish it or anything but taking a last few sips would put him out - while rocking. good luck

^^^ and if he was slightly fussy, we use "Gripe Water" night time version. It's a liquid that we get at Target. Put 2.5 ounces or so in a syringe and he loved it and it settled him down.