NY FRIEND CAT IS SUFFERING?

a friend of mine asked me to hold her cat, she lost her home and has nowhere to keep the cat, so she asked me to hold the cat until she find an apartment, since the cat has been at my home, it's been throwing up everything it eats, i've tried giving it IAMS hairball fomulated food,and four paws hairball remedy , and NOTHINGS working the cat is still throwing up and my rugs look horrible, whats should i do.