shuttle runs backed with bleep test type stuff.
5-a-side (proper 5 a side) is all about multiple fast sprints. You need a base fitness which stationary bike will help with but you need to be able to sprint, recover, sprint, recover, over and over for 2×7 mins.
If you’re talking about mates 5-a-side (60 mins, 34-all when the next group are lining up / next goal wins) then it’s all about sprints for the first ten minutes and then endurance.
(unless you play in goal like I did; in which case best preparation is to throw yourself onto concrete repeatedly and them have a mate smash balls at you from about 3 yards – aiming mainly at your nads and face)