It's not something they would ever find in the wild, so while it might not kill them, they are not hardwired to digest these foods and they wont do your tortoise any good. Fruit especially can be dangerous in large amounts; it gives tortoises diarrhea.
Russian Tortoises should be eating foods like spring mix (a mix of baby salad greens sold at most grocery stores) dandelion greens, or other dark leafy vegetables. "Leafy" generally refers only to salad-type vegetables.
This article has a good explanation as to what is good to feed tortoises and why:
My 3 russians get one carrot a month and that is all, otherwise they are eating grape leves, hibiscus leaves and flowers, radish tops squash leaves and flowers and such, little to no vegetables.
Vegetables make up about 10-15% of my Russian tortoises diet. I feed them everything available from squashes, pumpkin, eggplant, various beans, peas, corn, carrots and everything and anything else I can find. Tomato is actually a fruit and should not be a part of their regular diet however an occasional piece of fruit is not going to do any harm.
Vegetables are a good source of necessary vitamins.