we bring detergent (the single use packages), & fabric softener sheets as the studios don't have any (you can buy some in the laundry room, i think the single use tide is about $1; no charge to use the washers & dryers).
also, additional coffee, filters (basket, flat bottomed type), sugar/sweet n low, tea, salt & pepper.
we find the hangers sufficient for 2 people (not sure exactly how many, guesstimate about 8-10). there is an iron & board in the closet. (also a vacuum, blanket, sheet set & pillows for sofabed).
you will receive 4 towels, at least 4 (we always wind up with lots more

) handtowels, & 4 washclothes, as well as 2 dishtowels & dishwashing liquid by kitchenette. garbage bags are also provided. they will exchange the towels on your trash & towel day, as well as on your full housekeeping day.
they have the small bottles of shampoo, conditioner, & moisturizer (i bring my own shampoo tho). you will start with at least 2-3 soaps. you can ask mousekeeping at anytime for additional shampoo, soap, etc at no cost (except for tip, of course

MK has often just handed us bunches when we greet them in hallway, might be a YMMV tho

). there is a charge for additional towels.
the room comes with glass cups, ceramic coffee mugs, paper plates & bowls, as well as utensils. there is a hairdryer, but again, i bring my own (it dries faster).
we buy milk (& sometimes, some of the above) when we're there.
other than that, we just bring our clothes, & pretty much a bit of everything in our home medicine cabinet

(bandaids, moleskin, sunscreen, toothbush & paste, tylenol, etc)
hth
