The type of food appropriate to your tortoise depends on the species. (I don't think you mentioned the species - maybe I missed it.)
Sulcatas and leopard tortoise like grasses, russians and hermans like broad-leafed weeds, redfoots can consume fruits, and hingebacks like fruits and some animal matter, for example.
Spinach is one of those foods that is often considered less than desirable. It contains a substance called oxalic acid, and this substance binds with calcium and inhibits its absorption in the gut. But many recommended foods like dandelion or collard greens have some oxalic acid in them. It's just that spinach has more than most. So don't make spinach a major part of the diet.
It's best to feed a varied diet. This way you get as many different vitamins and minerals as possible into your tortoise and avoid the shortcomings of any one food.
Check websites like www.tortoise.org
www.tortoisetrust.org
www.chelonia.org
(or is that www.chelonian.org ?)
For general information on the dietary needs of the species you keep.
I don't know about cilantro. Since it's a grocery green acceptable for humans, it's probably OK for tortoises in at least small amounts.