node.js: iterate through nested firebase JSON tree

I am trying to access a nested firebase tree from node.js as follows.

ref.forEach( function(snapshot0) {
    snapshot0.child("Meals").forEach( function(snapshot1) {                                                            
        console.log(snapshot1.val);
    });                         
});

And it will just always tell me that ref.forEach is not a function.

 TypeError: refPrices.forEach is not a function

I have defined these as follows.

var db        = admin.database();
var ref       = db.ref("users");

I have checked these answers

How do I iterate through a large dataset with Firebase / Node.js?

Iterating through nested firebase objects - Javascript

Iterate through nested JSON tree and change values

But I believe according to those my above code should be working, so I am really confused. Also, I have tried to replace forEach by a loop, but I get

TypeError: ref.length is not a function

so I cannot calculate the maximum value of the loop. I have also tried

ref.once("value", function(snapshot0) {
    snapshot0.child("Meals").forEach( function(snapshot1) {                                                            
        console.log(snapshot1.val);
    });                         
});

but in that case it throws the error

TypeError: snapshot0.forEach is not a function

so I pretty much still have the same problem. I cannot work out where my example is different from the links to the solutions above?

Edit: here is what my JSON tree looks like (as per Frank's request). I have only shortened the userID's a little bit.

"users" : {
    "ugkvjTuXW2" : {
        "Meals" : {
            "Meal_2" : {
                "priceHist" : [ null, 1, 1, 1, 1, 1, 1 ]
            },
            "Meal_3" : {
                "priceHist" : [ null, 1, 1, 1, 1, 10, 1 ]
            },
            "Meal_4" : {
                "priceHist" : [ null, 1, 1, 1, 1, 1, 1 ]
            },
            "Meal_5" : {
                "priceHist" : [ null, 1, 1, 1, 1, 1, 1 ]
            }
         }
    },
    "oJJ1Cojia2" : {
        "Meals" : {
            "Meal_2" : {
                "priceHist" : [ null, 1, 4, 4, 1, 1, 1 ]
            },
            "Meal_3" : {
                "priceHist" : [ null, 1, 1, 1, 1, 10, 1 ]
            },
            "Meal_4" : {
                "priceHist" : [ null, 1, 5, 1, 1, 7, 1 ]
            },
            "Meal_5" : {
                "priceHist" : [ null, 3, 1, 1, 1, 12, 1 ]
            }
         }
    }
}