You shouldn't. The cloud is just someone else's computer. You can mitigate things by encrypting a lot but there's no way you can't know they don't peek at your data.

So if you can't trust the company offering the service, you shouldn't do business with them. It's the same with food and food supplies: if they can't be trusted to serve/sell you stuff that doesn't make you ill, don't do business with them. Very simple.