Reddit reviews RPI Y20090-250.0 YPD Broth, 250g

Sugar and water is insufficient- cells need other materials to make proteins and such.

The urea is there as a nitrogen source, which is necessary for amino acid biosynthesis and can be used as an energy source. I'm not sure if ammonium can be used for energy, but it's also a source of nitrogen and the phosphate is another necessary nutrient (ATP = adenosine tri phosphate).

Apple juice has sugar, phosphate and sufficient trace amounts of peptides or other nitrogen sources for cells to grow.

For a kitchen media, I think the easiest thing to do would be to use yeast extract. Alternatively (and even easier) you could buy premade media mix. Looks like it's $37.50 for 5L worth of mix.

YPD Broth Powder, 250 Grams https://www.amazon.com/dp/B00I31SXAC/ref=cm_sw_r_apa_qKkqzbQ55N0AQ

Also- make sure you're sterilizing whatever media you make in a pressure cooker before using it. It's a poor man's autoclave.

Source: years of growing yeast in undergrad