Hi, 

Although AIIMS doesnt have any particular guidelines for dress code, but its advisable to go for simple clothes. 

Avoid wearing clothes with big buttons or pockets, caps, scarfs, high soled shoes etc

Avoid wearing any ornaments like earrings, bangles, bracelets etc or any other metallic ornaments. 

Avoid carrying any sort of electronics with you, watches, calculators etc. 

Its advisable to opt for simple light clothes to avoid any trouble during frisking process. 

All the best.