Supply Kits reduce the cost of missions by 25%, increase Crew XP by 50%, and award Bonus Rewards for completing Away Missions and Space Battles. Supply Kits can be bought with and their effects last for 24 hours.
When an Away Mission or Space Battle is completed, the crew used will receive 50% additional XP. However, this is inconsistently calculated and potentially bugged. Presumably it is intended to be 50% of the original XP reward, rounded down the the nearest integer; but sometimes it falls significantly short of 50% or even lands above 50%. This will not be received if the Mission or Battle is completed at Warp speed. Instead the player will receive Bonus Rewards of Federation Training Programs.
No additional Captain XP is awarded.
If a player runs a Mission or Battle at Warp speed, they will receive Federation Training Programs as Bonus Rewards instead of the Bonus XP they would have normally received.