Is cost of items delivered "COGS" or "reimbursed expenses"?

I operate a concierge business where I do shopping for clients, take care of cars (get gas, repairs, service), etc.  I charge them monthly based on my fee and all the money I spent for them (e.g. in purchasing items, paying for repairs, etc.).  Do I count "all the money I spent for them" as "reimbursed expense" or COGS?  Thanks