好きな食べものあり
This sentence is grammatically wrong. It must be 好きな食べものある or 好きな食べものあります. If my guess is correct, the "ari" u mean is a very colloquial way of saying that something is an option.
For example, u and ur friends are talking about what u want to have for dinner.
1. U can say 魚はどう? And ur friend may answer by saying あり, which means that fish is an option and your friend may consider eating fish for dinner.
2. Or u can ask 魚はあり? This is almost the same meaning as 1. when u say "how about fish?"