Just wanted to write some stuff that I usually bring to the gym;
shaker cup (usually has pre workout or post workout)
lifting belt (usually for leg days)
lifting straps (best for back day)
chalk (good alternative to straps)
headphones (or airpods)
my pre workout i keep in there (I use ryse godzilla, wrecked mango and citris, and almost every bucked up flavor
sometimes a change of shirt, this is super helpful if yall are hitting a tough back day or chest day and are super sweaty. I recommend doing this if you have problems with back acne.