I do fast in small things often but seldom the big water and bread thing. Sometimes it’s just not having something I’d like or having simple food without sauce, salt, gravy or anything nice on it. Or cutting out snacks and treats, or choosing water or simple thing over what I really want.
I live in UK so the abstinence from meat on Fridays is a given and I do that. The small things are sometimes just part of life, so passive (something I accept) and sometimes active (my choice). They aren’t always food and can be giving up activities in life or social media etc. or even choosing to read a spiritual book rather than a novel. Any act of self denial teaches you to fight sin or so I think anyway.