I’ve never sold at a craft market, but knowing your audience will help, so knowing who’s most like going to be there or the area you’re selling at helps, even your environment will be important for example if it’s often cold or will end up getting cold soon beanies, scarves, gloves, etc might sell more.
I think things that are usable/useful could do good like coasters, scrubbies, scrunchies etc along with cute amigurumi, I think amigurumi sells good in general like bee’s, octopus’s reversible octopus’s, etc in fact I think a comment in a topic I linked mentioned that chenille types of amigurumi sold well. (Of course if you do use chenille it’s probably important to mention that it does shed and that’s normal)
Also any holidays that are coming up would go good too depending on when this craft fair will take place, I know mother’s day is coming up and it is currently may/spring so perhaps things like roses or flowers will probably be good, seasonal things will go good too if it’ll be during the summer perhaps a cute amigurumi of a sun with sunglasses will be good lol
Honestly anything cute would probably sell well or things that are popular, I read a comment in another topic that mentioned selling something different from the booths near them helped sell like hotcakes (other booths sold blankets, etc and they were selling amigurumi)
Here’s some links about craft markets/fairs, not necessarily about what sells but some good advice that could get more sells, good customer service, safety/health, etc