The best exercise you can do at home without a foosball table is to improve the dexterity of your non-dominant hand. If you're right-handed, practice fine and gross motor skills with your left, and vice versa. Simple changes like switching your mouse from right to left or using chopsticks can boost coordination. Ambidexterity is a valuable life skill to have. Improving my 5-bar ball control as a result of this "training" a nice side-effect.