We were talking about kitchen stuff, and darned if we couldn’t figure out what the third canister was for. Flour, sugar, and ???
I feel the fool.
Salt
Tea
I don’t know if you are referring to specific cannisters , but I was curious. Why do cannisters come in threes. Turns out they also come in fours, but here’s some labeled ones.

Bourbon!
Your question sent me looking for vintage kitchen canisters online. Flour, sugar, coffee, and tea were common. Also a canister for grease.
Then I remembered that the aluminum canister set in my grandmother’s kitchen included a canister for grease. Though I seem to remember she used it for something different, which I can’t recall.
We had a grease container always but it wasn’t part of our canister set. That’s why I remember the tea container because it never held tea (or anything) in our house.
At my house it would be salt, sugar, and a vat of soy sauce or oyster sauce.
Tea or coffee. The usual graduated-in-size, largest-to-smallest, when it was four canisters were:
Flour, Sugar, coffee, tea.
I have a white canister with a blue windmill design that belonged to my grandmother. It says Rice on it, but she used it for something else. I can’t remember what the others in the set said. Maybe coffee and tea?
There are only two canisters in my set–flour and sugar.
I seem to recall flour, sugar, and cocoa. (Wooden canisters in different sizes, but unlabeled–the ingredients would be in plastic bags inside the canisters.). My parents didn’t drink coffee, and when I was growing up only drank prebagged tea.
Rice? Pretty sure my mom had a rice canister.
I have always had a rice cannister. But it’s Tupperware.
Lol, for me, I deal with rice in giant buckets, so a canister wouldn’t do. My family, growing up, had recycled a giant cylindrical tub from a restaurant to hold 50 lb bags of rice (or 2-25 lb bags). I still buy 10-15lb bags for myself.
Tea would be good 3rd option but that’s a big canister for one type of tea leaves.
My mother and grandmother both used a coffee can.
I don’t deal with rice in 50 lb. buckets, but I DO buy rice in the large brown natural fiber bags (10-12 lbs?), or very rarely, what’s in the bags at BJ’s Wholesale Club - which I think might be 20 lb. bags.
I use a large 15 oz. cat food can that gets tucked only a shelf in the freezer after pouring off the grease from whatever I’m cooking. When it’s full, I top it with a tight cover of foil and into the trash bin on trash day.
Admiring your avatar!
Back in the day, a lot of people didn’t have a big selection of tea in their house, and the canister would store Lipton’s tea bags as easily as loose tea.
We didn’t have a canister set. My mother used an old Nyafat can for sugar, and a fancy Dutch cookie tin for tea bags. (There’s one just like it in the movie FIREFLY.)