Hi There is a store in Israel that makes milkshakes from different chocolates/candies(most or all are kosher). The milk is definitely kosher and it is opened on shabbat therefore there is no kosher certification. I want to get a shake with only kosher products. What are the strict and lenient laws according to this?

ב"ה Shalom Since there is no supervision on this store, there are no strict or lenient laws, unfortunately. One simply CANNOT eat there. Where there is no supervision nobody can assure that no non- kosher ingredients are not added. Milk Shakes can be found in plenty of establishments with proper supervision and keeping of Shabbat. All the best