Look inside the bowl. Is the water level very high (near the rim)? If yes, you need to remove some water first. Pouring more liquid into an already full bowl will just cause an overflow. Use a small bucket or cup to bail water out into a sink or bucket until the bowl is about half full.
Unblocking a toilet with hot water is one of the most reliable DIY methods for clearing soft clogs. Here is everything you need to know about why it works and how to do it safely. Why Hot Water Works unblocking toilet with hot water