Work lunches for $7 the whole week? New job and I am not used to packing food

I'm really poor right now. It is self inflicted though as I got paid my accrued annual leave when I got fired. I thought it would last longer than it did especially with starting a new job after three weeks of unemployment. So I did not budget for it at all. Self inflicted or not either way I have to eat. I live at home but I have to buy my own food/ingredients.

I worked three days last week at my new job. Office building corporate life. I wasn't prepared due to hospitality jobs and eating free food. I bought work lunches and coffee in the morning. Now I'm uncomfortably low in money until I get paid. Coffee would normally be free Monday onwards but I didn't have the access keys to the office so it is just work lunch I'm worried about. Lunch is also the biggest meal I eat in a day as I don't like eating breakfast.

I have $7.50 in coins besides my bank account but it feels sensible to budget on these coins.

Can I buy ingredients to make office lunches? What do I make?

I hate tuna and eggs so those cheap options are gone but it's mostly the options I see online. $7.50 for lunches probably is plenty for a week but I'm not used to preparing my own lunch at all. I didn't even pack food in high school being a stressed kid and no appetite at school.