Because soccer is such a physically demanding sport, it is important to run endurance drills regularly to keep your team ready for the field. The best way to get speeds up is by adding sprints into regular team jogs. Try having the team jog 3/4 of the way around the field, then sprint the last (short) end before doing a second lap.
You can also try these drills to increase players' endurance.
1. Step Jumps.
After initial stretching and warm-ups, have each player stand next to a cone. As you blow your whistle, players will tuck knees to chest and jump vertically up and over the cone. Without spending too much time on the ground, they will jump back to the other side. Have them continue jumping for 30 seconds, doing at least 3 sets with a short rest in between.
1 4 Drill
2. Shuttles.
In addition to team practice, players can practice shuttle drills at home. Do this drill last in your practice, as it wears players out and can make legs dangerously weak. Place 5 cones in a line, with the total distance from first to last being 10 yards. The player starts at cone 1 and runs to 2 and back, then 3 and back, then 4 and back, then finally 5 and back. S/he should be in a flat-out sprint for the duration of the drill. Allow players to rest 30 seconds before repeating. Have your team do 2 sets of 3 shuttle runs each. Allow a more significant (2 minute) rest between the 2 sets.
Be sure to have the team cool down and stretch sufficiently after shuttle drills.