Can we legally drug test a 1099 or independent contractor that is working for our company? And if so, would we need to get some kind of consent from the candidate for it to be legal? And also, can we run a background check on a 1099 or independent contractor?

A contractor is not an employee; they are mutually exclusive.
You are free to ask for a drug test (not sure how you'd do it without consent; steal some hair? Divert a toilet?) and do a background check, but it sounds like you may be breaking the rules of what constitutes a contractor working for you. A 1099 contractor may not work at your place of business, use your equipment/furniture/computers etc, and must have other sources of income from yours. There are other requirements too. I've seen businesses charged by the IRS with years of back taxes and penalties for failing to pay wages with all the attending taxes, comp, unemployment, etc.