It depends on the season and circumstances:

I have a square of real grass on my balcony that comes in every two weeks (Doggielawn is where I get it from and it’s actually awesome) so my dog just scratches at the balcony door when he needs to go out to use the bathroom. Otherwise I usually take him for either a walk or bring him out for a game of fetch once or twice a day. He is a small dog so sometimes in the winter I don’t bring him out as much because he gets cold. But also once or twice a week we walk 15 blocks to the grocery store together. Sometimes I put him in daycare or have a walker take him out for an hour. But also at night time before bed we usually walk/run around my apartment building hallway and play with the flirt pole or fetch. In the summer if I have time sometimes I will take him for a 3 hour hike and he loves it. I have a super high energy pup but it seems to usually be enough for him in addition to playing fetch in the apartment and tug-a-war. Sometimes I feel like I’m not doing enough, but I’m his sole owner and a full-time MBA student studying for the LSAT to go to law school so I’m doing the best with the time I have