SOQL gives (null <object__r>) output for the lookup type field value in salesforce?

I have two objects, Sdf__c and SdfBudget__c. Sdf__c has a lookup field related to the SdfBuget object. I want to fetch values from sdf__c along with budget fields from sdfBudget that match SdfBudget vbu names.vbu is a formula field (text).

But i return (null <object__r>) for the field. How to get the value instead of null.

The field has values but its not returning.

suppose the table has the following columns: Sdf__c

SdfBudget__c

and i need to get the output as follows

Query which i have trid

    List<SdfBudget__c> sdfVbus=new List<SdfBudget__c>();
    sdfVbus=[SELECT budget__c,VBU__c FROM SdfBudget__c WHERE VBU__C != null];
    List<Sdf__c> sdfItems=new List<Sdf__c>();
    for(SdfBudget__c ob:sdfVbus)
    {
        vbuValues.add(ob.VBU__c);
    }
   sdfItems=[SELECT Name,VBU__c,Sdf_Budget__r.Budget__c FROM sdf__c WHERE VBU__c IN :vbuValues];

Another thing is that while trying to debug it in anonymous window. the field is not being logged.

system.debug('sdfItems>>>'+sdfItems);  

This is how i got the result,

    Map<string, Decimal> sdfBudgetMap = new Map<string, Decimal>();

    sdfVbus=[SELECT budget__c,VBU__c FROM SdfBudget__c WHERE VBU__C != null];
    for(SdfBudget__c ob:sdfVbus)
    {
        sdfBudgetMap.put(ob.VBU__c,ob.budget__c);
        vbuValues.add(ob.VBU__c);
    }
 sdfItems=[SELECT Id,Name,VBU__c FROM sdf__c WHERE VBU__c IN :vbuValues ];
    for(Sdf__c item :sdfItems)
    {
    ---------------------
    -----------------------   
    model.Budget=**sdfBudgetMap.get(item.VBU__c);**
    --------------------------------------
    }