It pains me to say it but it can’t be done. Premium Minecraft servers would try to authenticate users on Minecraft servers which is something Cracked clients can not do simply because they don’t exist in official Minecraft database.
It’s still possible to use website that allows sharing Premium Minecraft accounts or even buy cheap second hand Minecraft accounts but as you can imagine that’s really not a good idea. You will never know when you will lose access to your “premium” Minecraft account.
What can you do?
Aside from keep playing Cracked Minecraft Servers and save up some money for premium Minecraft account there really isn’t much you can do. There are actually quite a few nice cracked servers out there but in most cases you won’t be able to get skins and capes, not without real Minecraft account.