There are problems with food from a vegan restaurant.
See this Chabad site
A vegan restaurant would not have a hard time getting kosher
certification. However, as long as there is no such certification one
should not eat there. There are many reasons why a strictly vegan
establishment requires kosher certification. Here are a few of them:
It is possible for a minute quantity of animal products to be included in a vegan-certified food. According to the Vegan Society, an
outfit which licenses vegan foods, "vegan products must, as far as is
possible and practical, be entirely free from animal involvement."
Furthermore they state, "Animal products are sometimes used in
instances that are not immediately obvious."1
All utensils used to prepare kosher food, as well as countertops, ovens, etc., must be kosher. Meaning, if they were previously used for
non-kosher foods, they must be koshered before being used for kosher
Wine and grape juice are not kosher unless they are certified kosher (see Wine and Grape Products). Even if the restaurant doesn't
have a wine list, many dishes include wine or grape juice in their
4. Certain foods must be cooked or baked by a Jew in order to be kosher (seeBaked and Cooked Foods). (Doesn't apply in your case - no cooked food)
And see this site which points out:
Unfortunately for vegans[and Kashrus observers], avoiding all animal
byproducts — especially bugs– in the American food system is basically
impossible. The Food and Drug Administration even keeps a list of how
many bugs and bug parts manufacturers are allowed to have in their
products — including many that vegans or vegetarians [and Jews] eat.
So how much non-vegan/[non-kosher content] might be in your food? We
had a look at the standards and, leaving aside how much animal feces
and hair is allowed, compiled 10 of the grossest.
Frozen or canned asparagus Producers are allowed to leave 6 or more attached asparagus beetle eggs and/or sacs on 10% of their spears and
either: an average of 40 thrips per 100 grams; or make sure the
remaining insects or insect parts have an average aggregate length of
7mm or longer per each 100 grams. Crunchy!
Canned lingonberries They taste so good at Ikea — but that little extra protein comes from the 3 larvae per pound allowed.
Frozen Brussels sprouts Look closely: producers can have up to 30 aphids or thrips in every 100 grams.
Canned orange juice Tangy! Producers are allowed 5 fruit fly and other fly eggs or 1 maggot in each 250 milliliters.
Canned corn Each 24 pounds of corn can have up to two corn ear worms or corn borer larvae less than 3 millimeters or longer, as long
as the total larvae, shed skin or fragments thereof does not exceeds
12 millimeters. - See more at: