Free · nothing to sign up for
20 things you can pick up on one grocery run, and none of them need cooking. Print it, or keep it on your phone.
One page · no email needed · free
The same 20 things on one page, in a printable PDF. No email, no sign up.
The other half of the problem
Knowing what to bring is the easy part. The free snack sign-up sheet is one link the whole group fills in, so you are not the person chasing everybody.
Make a snack sign-up sheet →Free, and nobody needs to log in.
Clementines, pretzels or yogurt tubes. None of them need cooking, one bag covers a whole team, and they survive a hot car.
Water, cups and napkins, a cooler, trash bags and wet wipes. The easiest things to forget, and the most useful things to turn up with.
Ask before you plan anything, write it at the top of the list everybody can see, and default to nut free with a group you do not know well.