> I don't want McDonald's to know if I've ever eaten at McDonald's. Call me crazy,

You are crazy.

Back in the good old pre-Internet commerce days, when you'd go in person to a store, you did not have a reasonable expectation that the owners/employees will forget you once you're gone. If you didn't want the owner/employees to know, you'd get someone else to go in on your behalf.

If you don't want McDonald's to know, get someone else to buy for you.