Do not get one of those drawstrings bags! They will dig I to your shoulders over a trip if you have anything of weight like water bottles.

Get something with multiple zipper pockets so you can organize your stuff in, so you aren't fumbling through everything to find 1 thing. Bonus to have a separate pocket for water bottles that sweat and get everything else wet.

Also, get something with a chest clasp that connects the backpack across your chest so it is not constantly pulling on your shoulders or sagging.

As someone who travels a lot, I have a day pack I always also take for exploring new areas where I am out all day and these little features make a big benefit.

Water resistant is also nice for days when it rains and you just have on a rain jacket so no need for poncho to cover it.

I do have a bb8 backpack I had to buy at mouse gear when my last drawstring bags rivets ripped out too.

Something with these features, not sure of brand

Daxvens Day Hiking Backpack with Chest Wasit Strap for Men Women Youth, 25L Small Lightweight Water-Resistant Daypack Carry-On Camping Climbing Trekking Cycling Commuter https://www.amazon.com/dp/B06Y42RS49/ref=cm_sw_r_cp_apa_i_MT0UCbCBF507E