The best way to build your abs, is in my opinion to do push-ups and
sit-ups. But when do you have time for these? Let's see.

1. While watching tv. It's great to do some sit-ups while watching
your favourite series on tv. Time flies and you don't even notice that
you are exercising!

2. In bed. This might not be a good idea if you are really sleepy. But
I like to do this if I am not so tired when I go to bed. I'm sure that
you will be after few hundred sit-ups. The only minus here is that
your bed is gonna be pretty sweaty..

3. At work. Eh, really depends on where you work. Might not be a good
idea in most of the workplaces, really depends on what you do and
where. I work at home. It's perfect to do some push-ups when I have my
break.

4. Sauna. Well, most of you probably don't have a sauna. But In my
country there are plenty. You are already sweaty in sauna and there is
nicely warm so it's perfect place to do some sit-ups. Just watch out
not to get fainted!