Hi Ben, I would pop down to a local farm or tyre place and get some tyres from there- they won’t mind you taking them at all. I would also go to the local forrestry commission and see if you can get logs from there, again they should be glad to help as it is getting re-used.
Cut some holes in the logs and feed some old climbing rope through (again pop across to a local climbing centre and see if they have old rope that can be cut up).
Local Army surplus stores do the old kit bags that can filled with sand (make sure you put it in a plastic bag first and use gaffer tape to wrap it up tight).
As Ash says there is lots you can do with bodyweight- try this…
Player 1 lays on his back with his hands clasped creating a loop with his arms.
Player 2 gets on all fours (balls of feet and hands) and uses the loop of player 1 around the the back of his neck. player 2 then keeps a low body position and drives forward staying on all fours and dragging player 1. It’s hard and the boys will love it.
You can do all sorts from that with player 1 holding a ball as he is being dragged, whistle blast then player 2 stops dragging and rips the ball from player 1.
I tend to use the tabata intervals with bodyweight exercises such as clap press ups, up downs, squat thrusts, firemans carry, baby carry, ball wrestles with short sprints.
Have fun mate especially when you improvise with things around the club.
Oh, try this one for body position and core-
Player gets down in good low body position, places hands on top of a rucking shield and then drives it forward. Now if they push down with their hips up too high they will not move and find it difficult (funny when this happens). When they get the right body position and a stronger core to hold themselves up they will glide along the grass.
Hope you can understand that mate and let us know how you get on and more importantly what you come up with…lol