Fill in Missing Dates

I have a table of weekly values that I want to break out into daily values.

Data is similar to below but is in Excel.

CREATE TABLE #tempTable (
Brand VARCHAR(100),
Date DATE,
Spend int)

INSERT INTO #tempTable
(
    Brand,
    Date,
    Spend
)
VALUES 
('A', '1/7/2021', 100),
('A',  '1/14/2021', 150),
('A', '1/21/2021', 200),
('B', '1/7/2021', 250),
('B', '1/14/2021', 200),
('B', '1/21/2021', 900),
('C', '1/7/2021', 200),
('C', '1/14/2021', 100),
('C', '1/21/2021', 50)

SELECT
	*
FROM #tempTable

I want to generate records for every day in between the available dates for each Brand so that the end result looks like this:

I found this suggestion on in an old StackOverflow post, but it only works to create a table with just Date and Spend.

FullTable = 
ADDCOLUMNS(
    CALENDAR(MIN(#tempTable[Date]), MAX(#tempTable[Date])),
    "Quantity",
    LOOKUPVALUE(
        #tempTable[Spend],
        #tempTable[Date],
        MAXX(
            FILTER(#tempTable, #tempTable[Date] <= EARLIER([Date])),
            [Date]
        )
    )
)

Does anyone have any idea how to expand it to include an additional dimension?