Most bags, especially most free sanding bags, don't take hits like people get hit.

Foam is also bad, and in my opinion so are the very hard traditional 'sawdust' or whatever heavy packed bags.

I am much more of a fan of water bags, especially quality ones with some baffles AND some small padding which can combine to make it react much closer to a human being -- after all, we are 90% plus water and we move some when we get hit (hard enough.)

But hey, you got to make do with what you can afford, store, have etc. As always be careful, wrap your hands, and use the equipment within the limitations you know it has (and learn those limitations carefully at first.)