Currently I have a bag that holds up to 1000 items which is currently at 988 items just now.
Max Revive 1
Incense 5
Raid Pass 1
Star Piece 3
Gift 5
Poke Ball 5
Great Ball 188
Ultra Ball 752
Lure Module 3
Golden Razz Berry 1
Silver Pinap Berry 12
Sun Stone 2
Kings Rock 2
Metal Coat 2
Dragon Scale 2
Up-Grade 2
I constantly have to delete poke balls, potions and berries just to keep spinning Pokestops.