For smaller expenses, such as lunch for the office, miscellaneous supplies, and unexpected minor expenditures, many offices maintain a petty-cash drawer or box. This system can work very well if it is not abused, you keep careful records, and only one person has control of the funds.
As available petty-cash funds are depleted, request a new check to replenish the funds. Include receipts and a summary sheet that reflects the detail of each expense and adds up the amount requested. Doing so allows funds to be available consistently, and the documentation provides a good backup for monies spent.