Walking home every day. It's about an hour or so, vs my 20 mins on public transport, but it's become a good time of meditative reflection and has provided me with some fitness benefits. It's also time I'd otherwise spend just reading the internet or playing a videogame anyway.

Also, trying to meal prep a large number of the same dish to avoid buying lunches during the week and thus spending a large amount of money needlessly. I don't mind eating the same thing for several days, though to avoid that you'd just need to prep 2 or 3 meals of smaller size. It doubles as an effective way to portion control too, since I can use containers of a specific size. It also means that many nights of the week I get home from my walk and just toss one in the microwave or oven to reheat and don't end up eating any later than normal.

Edit: Both of the above have helped me maintain my post-glandular-fever weight loss of about 14kg, which has left me feeling significantly healthier than I was previously. Occasionally I blow out with a weekend of debauchery involving way too much alcohol and unhealthy food, but the walking then chips that back down and gives me motivation to limit said blowouts as I now have a quantifiable amount of effort that it equates to.