Consuming caffeine with creatine negates the strength gains afforded by the latter, according to several studies. Caffeine inhibits the transport of creatine into muscle. The best way to avoid this is by waiting at least 4 hours after your morning joe to take the supplement. If you are in a loading phase, limit caffeine intake altogether for at least 1 week. Once the creatine is safely stored, no amount of coffee can steal it from you.
Integrative Pharmacology 