What are you looking for, exactly ?
A quick spreadsheet that you don't intend on sharing or using on another system - Numbers.
A quick speadsheet that you want to share and have access to from anywhere - Google Drive or OneDrive. Google is much faster to open but I find working with their spreadsheet on a tablet a PITA.
A (nearly) full blown Excel compatible application that doesn't mangle your documents - CloudOn. But it's slow to start, has a difficult navigation interface, and I believe requires an internet connection to even start a new document.
Unfortunately there seem to be no quick, fully Excel compatible office like OfficeSuitePro on Android. Yet.