var sellableItemId = "myid"
SellableItem item = container.SellableItems.Where(x => x.Id == sellableItemId ))..FirstOrDefault()

return item.ItemVariations;

"57042066|57042067|57042068|57042069|57042070"

var variantId = "57042066";
var variant = container.SellableItems.Where(x => x.Id == variantId));