Is it recommended for small businesses? And does 13.9% APR for a $100,000 loan worth it?

I'm applying for a $20k Corporate Credit Card and a loan for business expenditures but should I sign myself as the guarantor?

Is it recommended for small businesses?

Of course, if your business needs a credit card it's the kind to get.

And does 13.9% APR for a $100,000 loan worth it?

Probably not. For a $100,000 loan that's a lot of interest. For a credit card it's fairly reasonable. Not low, but not that bad. But same as with an individual, a credit card account isn't usually the best option for long-term financing of a large amount of money.

should I sign myself as the guarantor?

If you can avoid it, no. But you probably can't avoid it.