I haven't spent that much money today, as my lunch was provided by the office, so I only bought a snack duringwhen I was walking around the office after lunch. I haven't spent that much money today, as my lunch was provided by the office, so I only bought a snack when I was walking around the office after lunch.

I haven't spent very much money today, as my lunch was provided by the office, so I only bought a snack duringwhile walking around the office after lunch. I haven't spent very much money today, as my lunch was provided by the office, so I only bought a snack while walking around the office after lunch.

If we want to be precise, I don't you actually bought the snack while you were walking around the office. So, maybe it should be "so I only bought a snack that I ate while walking around the office after lunch"

I haven't spent much money today, as my lunch was provided by my office (or: my workplace), so I only bought a snack duringwhile I was walking around the office after lunch. I haven't spent much money today, as my lunch was provided by my office (or: my workplace), so I only bought a snack while I was walking around the office after lunch.

I haven't spent much money today, as my lunch was provided by office, so I only bought a snack duringwhile walking around the office after lunch. I haven't spent much money today, as my lunch was provided by office, so I only bought a snack while walking around the office after lunch.