We normally bring a sandwich or last night's leftovers to work for lunch, as there's very little you can get locally that you can be confident about eating!
I'll sometimes send the driver out to get me something though... The omelette sandwiches are not too bad, or you can get some little donut-type things that are fairly nice. I've recently discovered fresh corn-on-the-cob which is lovely, and of course bananas, papaya, and avocados are cheap and readily available... (although you do have to be careful of the quantity. Soon after moving to Kumasi from Accra, before I had chance to get used to the cheaper prices up here, I gave one of the drivers 2 Ghana Cedis (about £1) and asked him to go and get 'a few bananas - for about six people' for a meeting we were having. Ten minutes later, he duly came back with a tray piled with about 20 bananas, with the same again left in the kitchen!)
So on Friday I sent the driver out to get some corn and a papaya, or pawpaw as they call it here. I came back toi my desk a little later to find the corn but no pawpaw, thought nothing of it, got in the car at the end of the day and my driver turned round with his sneaky little cheeky smile and pointed to the most enormous piece of fruit I have ever seen wedged between the seats!