There's a few spots to sit and eat your own sandwich. I don't remember seeing a cafe but that doesn't mean that there could be one in there..
There is only a vending machine area. You can have your own food.
They have a dining area in the building but I'm not sure if they have lunches available for purchase. I did know that if you take a lunch, it's best to leave it in a cooler in your car because they don't want you carrying too much in the museum.
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